Book of ABSTRACTS

7th Italian-Japanese Workshop on
Liquid Crystals
and
10th National meeting
of the Italian Liquid Crystal Society
SICL
JLCS
2014
Book of
ABSTRACTS
Istituto Biblioteca Classense- Ravenna (Italy)
7-10 July 2014
Organizing Committee
Italy
G. Assanto (Università “Roma Tre”)
G. Abbate (Univ. di Napoli “Federico II”)
R. Asquini (Univ. “La Sapienza”)
A. d’Alessandro (Univ. “La Sapienza”)
R. Bartolino (Università della Calabria)
T. Bellini (Università di Milano Statale)
C. Chiccoli (I.N.F.N. Bologna)
G. De Luca (Università della Calabria)
G. Galli (Università di Pisa)
L. Marrucci (Univ. di Napoli “Federico II”)
D. Pucci (Università della Calabria)
P. Pasini (I.N.F.N. Bologna)
F. Simoni (Univ. Politecnica delle Marche)
G. Strangi (Case Western Reserve Univ., USA)
E. Virga (Università di Pavia)
C. Zannoni (Università di Bologna)
Japan
T. Ikeda (Chuo University)
T. Kato (University of Tokyo)
N. Kawatsuki (University of Hyogo)
H. Kikuchi (Kyushu University)
K. Kishikawa (Chiba University)
N. Koide (Tokyo University of Science)
S. Kurihara (Kumamoto University)
S. Kutsumizu (Gifu University)
I. Nishiyama (DIC)
M. Ozaki (Osaka University)
T. Sasaki (Tokyo University of Science)
T. Seki (Nagoya University)
Y. Shimizu (AIST)
Y. Tabe (Waseda University)
H. Takatsu (DIC)
J. Yamamoto (Kyoto University)
Monday, July 7
SICL-JLCS
8.30-9.30
Session I at the City Hall Address: Piazza del Popolo 1
Registration and welcome
address
9.40-10.05
Tommaso Bellini
10.05-10.30
Masanori Ozaki
10.30-10.55
Giuseppe Chidichimo
10.55-11.15
Coffee break
Session II at Classense
Institute
11.15-11.40
Jun-ichi Hanna
11.40-12.05
Valentina Domenici
12.05-12.30
Hirotsugu Kikuchi
12.30-12.55
Roberto Caputo
13.00-15.00
Lunch
Session III
15.00-15.25
Isa Nishiyama
15.25-15.50
Claudio Zannoni
15.50-16.15
Yuka Tabe
16.15-16.40
Pierangelo Metrangolo
16.40-17.00
Coffee break
Session IV
17.00-17.25
Jun Yamamoto
17.25-17.50
Ugo Zammit
17.50-18.15
Takeo Sasaki
Origin and propagation of chirality in DNA
liquid crystals
Non-peripheral substituted phthalocyanine
with high carrier mobility and its solar cell
application
Advanced multifunctional materials based
on liquid crystal thienoviologens
Address: Via Baccarini 3
(Sala Muratori)
Highly ordered smectic liquid crystals for
organic field effect transistors
New composites based on liquid crystalline
elastomers for micro-actuators and energy
storage systems
Structural analyses of liquid crystal blue
phases
Active plasmonics: systems design and
characterization
Induction of birefringence in optically
isotropic liquid phase of chiral mesogenic
compound
Multiple scale modelling and simulations of
liquid crystals
Heat-driven unidirectional rotation of
cholesteric LC droplets
Halogen-bonded liquid crystals, gels, and
polymers
Second order phase transition in hyper
swollen lyotropic liquid crystals
Photopyroelectric calorimetry for the
thermal and optical evaluations of light
induced transitions in liquid crystals
Dynamic amplification of optical signals in
photorefractive ferroelectric liquid crystals
Tuesday, July 8
SICL-JLCS
Session V
8.45-9.10
Junji Watanabe
9.10-9.35
Alberta Ferrarini
9.55-10.0
Hideo Takezoe
10.00-10.25
Nicolas Godbert
10.25-10.50
Nobuhiro Kawatsuki
10.50-11.10
Coffee break
Session VI
11.10-11.35
Rita Asquini
11.35-12.00
Shoichi Kutsumizu
12.00-12.25
Francesco Simoni
12.25-12.50
Takahiro Seki
12.50-13.15
Giuseppe Strangi
13.15-15.00
Lunch
15.00-19.00
Social Program
Ravenna city tour and visit
to mosaics
20.00 Social dinner
High-HTP macrocyclized phenyl cinnamate
dimer utilizable as photo-responsive chiral
dopant for nematic liquid crystals
Molecular geometry, elastic constants and
twist-bend nematic phase
Structure-sensitive bend elastic constants
between pN and sub-nN
LCDiXRay: A user-friendly program for the
indexation of columnar liquid crystals
PXRD Patterns
Comparison of molecular orientation
structure of photoalignable liquid
crystalline polymer films at the near-surface
and in bulk
Liquid crystal channel waveguides for
optofluidic applications
Phase structure and transition mechanism
in azobenzene-containing bicontinuous
cubic liquid crystalline systems.
Electric field tuning of optoelastic trapping
in nematic liquid crystals
Photoalignment of liquid crystalline
polymers commanded from the free surface
Lasing in liquid crystals driven to chaos:
plasmon-exciton coupling enhances
scattering and gain
Wednesday, July 9
SICL-JLCS
Session VII
9.00-9.25
Tomiki Ikeda
9.25-9.50
Stefano Turzi
9.50-11.00
11.00-11.25
Joint Poster Session
Coffee break
11.25-11.50
SICL
Session I
Romeo Beccherelli
11.50-12.15
Giovanni Gilardi
12.15-12.40
Maria Enrica Di Pietro
12.40-13.00
Francesca Serra
13.00-15.00
Lunch
Session II
15.00-15.25
Luiz R. Evangelista
15.25-15.50
Hideo Takezoe
15.50-16.10
Otello Maria Roscioni
16.10-16.30
16.30-18.30
Coffee break
SICL Assembly
Photomobile Polymer Materials: Structures
and Functions
Orientational order parameters for lowsymmetry liquid crystals
Liquid crystal tuneable plasmonic devices
Lightwave circuits based on organic
materials for optical signal filtering and
switching in WDM communication systems
NMR in different partially ordered media: a
route for structure, order and conformation
of small flexible organic compounds
Inducing topological defects by curvature
and edges for tunable colloidal assembly in
nematic liquid crystals
Electrical response of a confined isotropic
liquid sample: biological systems and liquid
crystals applications
Azo-dendrimer
for
manipulating
microparticles
Molecular organisation in nematic liquid
crystals close to a solid surface
Thursday, July 10
SICL
Session III
9.00-9.20
Maria Penelope De Santo
9.20-9.40
Alfredo Mazzulla
9.40-10.00
Antigone Marino
10.00-10.20
Giovanna Palermo
10.20-11.00
11.00-11.20
Coffee break
Federica Ciuchi
Giuseppe Pucci
11.20-11.40
Mario Cifelli
11.40-12.20
Final remarks and
conclusions
Lunch
Visual
micro-thermometers
for
nanoparticles photo-thermal conversion
Optical trapping of chiral microresonator
Ellipsometric study of nematic alignment on
silicon oxides for displays
Plasmonic nano-heaters confined in selforganized materials
Alignment of chromonic molecules
Order reconstruction in turbulent nematics
Translational self-diffusion in liquid
crystals by means of NMR diffusometry:
Recent advancements
SICL-JLCS WORKSHOP
TALKS
Origin and propagation of chirality in DNA liquid crystals
Tommaso Bellini
Dipartimento di Biotecnologie Mediche e Medicina Traslazionale
Università degli Studi di Milano, Milano, Italy
Predicting the chiral behavior of cholesteric phase on the basis of the molecular properties is
notoriously a very difficult task. This problem was recently tackled by a combination of
experiments and theory for the case of the chiral nematic ordering that develops in concentrated
solutions of DNA oligomers [1-4]. In these systems the formation of liquid crystal phases is
mediated by the end-to-end aggregation of DNA duplexes into columns of chemically distinct but
physically continuous duplexes. The chirality of the DNA double strands gives rise to a
macroscopic helical precession of molecular orientation, whose handedness and dependence on
concentration and temperature follows a complex pattern difficult to unravel [2-4].
DNA cholesterics are a particularly convenient system to study the propagation of chirality. The
molecular structure of the B-DNA helices is symmetric and very well known, and its chirality is
very explicit. Moreover, while in typical lyotropic and thermotropic cholesterics the monomers
have a fixed chirality given by the molecular or colloidal structure, the self-assembly of DNA can
be exploited to modify the structure of the aggregated columns, tuning the chirality of the columnar
aggregates and study its effect on the collective ordering.
Experimental results [3] indicate that once the pair interactions between helices is given, the
propagation of chirality follows simple rules that take into account column length distribution and
the continuity of the helix within each column. All difficulties in interpreting the nematic ordering
of chiral molecules are actually nested in the determination of the torque resulting from pair
interactions, as indicated by theoretical investigation performed via molecular theory and coarse
grained model of the torque between helices [4]. Indeed, the sign of the torque experienced by
neighboring DNA helices depends on the balance on their average distances, in turn depending on
the overall concentration at which the nematic phase can be found. These facts enable interpreting a
large quantity of otherwise bizarre chiral behavior observed in DNA liquid crystals.
References
[1] M. Nakata et al., Living Polymerization and Liquid Crystal Condensation of 6-20 Base Pair DNA Duplexes, Science
318, 1276, 2007
[2] G. Zanchetta et al., Right-handed double-helix ultrashort DNA yields chiral nematic phases with both right- and
left-handed director twist, Proc. Natl. Acad. Sci. U.S.A. 107, 17 497 (2010)
[3] M. Rossi et al., Propagation of Chirality in Mixtures of Natural and Enantiomeric DNA Oligomers, Phys. Rev. Lett.
110, 107801 (2013)
[4] E. Frezza, F. Tombolato, and A. Ferrarini, Right- and left-handed liquid crystalline assemblies of oligonucleotides:
phase chirality as a reporter of a change in non-chiral interactions? Soft Matter 7, 9291 (2011).
Acknowledgment: Effort sponsored by the Italian Ministry of Education, Universities and Research, PRIN project
Non-peripheral Substituted Phthalocyanine with High Carrier
Mobility and Its Solar Cell Application
Masanori Ozaki1, Makoto Yoneya2, Yo Shimizu3, Akihiko Fujii1
1 Graduate School of Engineering, Osaka University, Yamada-oka, Suita, Osaka 565-0871, Japan
2 Nanosystem Research Institute, AIST, Umezono, Tsukuba 305-8568, Japan
3 Research Institute for Ubiquitous Energy Devices, Kansai Center, AIST, Ikeda, Osaka 563-8577, Japan
e-mail: ozaki@eei.eng.osaka-u.ac.jp
Liquid crystal is one of the promising materials as an organic semiconductor because of the
potentially high carrier mobility comparable to that of a-Si (0.1 cm2/Vs). We have demonstrated a
high carrier mobility in excess of 1 cm2/Vs in non-peripheral substituted phthalocyanine,
1,4,8,11,15,18,22,25-octaoctylphthalocyanines (C6PcH2) [1]. C6PcH2 shows a unique temperature
dependence characteristics of the carrier mobility which must be related to the phase structure of
this material. We have also demonstrated a high-efficient bulk-heterojunction solar cell based on
C6PcH2 [2]. The device can be fabricated through a spin-coating process from the blend solution of
C6PcH2 and 1-(3-methoxy-carbonyl)- propyl-1-1-phenyl-(6,6) C61 (PCBM). For the formation of
the optimally phase-separated nano-structure for efficient carrier generation and transportation, the
mesogenic properties should play an important role. Solar cells have demonstrated a high external
quantum efficiency above 60% in the Q-band absorption region of C6PcH2 and a high energy
conversion efficiency of 3.1%. By inserting appropriate buffer layers between the electrodes and
active layer and by incorporating additives such as 1,8-diiodooctane (DIO) into active layer for
morphorogy optimization, the fill factor FF and energy conversion efficiency were improved to be
0.55 and 4.2%, respectively [3, 4]. As a donor material in the BHJ solar cell, we used a binary blend
of CnPcH2 derivatives and investigated a device performance upon changing a ratio of components
in the blend. The highest power conversion efficiency was demonstrated for a C5PcH2
concentration of 25mol% in C5PcH2/C6PcH2 blend, which exceeded those of solar cells utilizing
pure Pc of C5PcH2 or C6PcH2 as a donor material. This result indicates a possibility of the device
performance optimization of the solar cell upon using a blend of liquid-crystalline semiconductors
as a material of active layer, as the same manner as the LC blends for the optimization of LCD
performance [5]. We also investigated blend effect of C6PcH2 and polymer semiconductor for the
improvement of long-wavelength sensitivity in the bulk hetero-junction solar cells. The effective
broadening of the wavelength range of the solar cell has been achieved by the use of the
polymer/C6PcH2 blend as a p-type semiconductor [6].
References
[1] Y.Miyake, et al., “High Carrier Mobility up to 1.4 cm2·V-1·s-1 in Non-Peripheral Octahexyl Phthalocyanine”, Appl.
Phys. Express, vol. 4, p. 021604, 2011.
[2] T. Hori, et al., “T Solution Processable Organic Solar Cell Based on Bulk Heterojunction Utilizing Phthalocyanine
Derivative”, Appl. Phys. Express, vol. 3, p. 101602, 2010.
[3] Q.-D. Dao, et al., “Efficiency enhancement in mesogenic-phthalocyanine-based solar cells with processing
additives”, Appl. Phys. Lett., vol. 101, p. 263301, 2012.
[4] Q.-D. Dao, et al., “Effects of processing additives on nanoscale phase separation, crystallization and photovoltaic
performance of solar cells based on mesogenic phthalocyanine”, Organic Electronics, vol. 14, p. 2628, 2013.
[5] H.Fukui, et al., “Miscibility in binary blends of non-peripheral alkylphthalocyanines and their application for bulkheterojunction solar cells”, Organic Electronics, vol. 15, p. 1189, 2014.
[6] T. Hori, et al., “Non-Peripheral Octahexylphthalocyanine Doping Effects in Bulk Heterojunction Polymer Solar
Cells”, Organic Electronics, vol. 13, p. 335, 2012.
Acknowledgment: This work was partly supported by Grants-in-Aid for Scientific Research from the Ministry of
Education, Culture, Sports, Science and Technology, Japan, and by Advanced Low Carbon Technology Research and
Development Program from the Japan Science and Technology Agency (JST-ALCA)
Advanced Multifunctional Materials Based on Liquid Crystal
Thienoviologens
Amerigo Beneduci1, Sante Cospito1, and Giuseppe Chidichimo1
1. Department of Chemistry and Chemical Technologies, University of Calabria, Via P. Bucci, 87036 Arcavacata di
Rende (CS), Italy
e-mail: giuseppe.chidichimo@unical.it
The research in the field of electronic and photonic devices based on ordered organic
semiconducting materials has been boosted by the development of new multifunctional materials
[1-3]. The order characterizing liquid crystals has been exploited for improving charge mobility
performances [2]. However, while in the last decade much effort has been addressed to the
synthesis of hole-conducting materials (p-type), less attention has been paid on the development of
electron-conducting ones (n-type). Here we show the bulk multifunctional properties of conjugated thienoviologen ionic liquid crystals [4] which have strong electron acceptor character
and exhibit high fluorescence in the bulk state ( up to 68%). Notably, the combination of their
optical properties with high ionic conductivity [5] and fast intermolecular electron transport, leads
to their unique electrochromic and electrofluorochromic functions (Fig. 1) [6]. In addition to the
above properties, these materials show photoconduction in glassy LC state at room temperature.
The photoconductivity can be related to the reduction of the ionic liquid crystals, opening the way
to the use in wider range of advanced optoelectronic devices [7]. Furthermore, phase separation
processes in mixtures of these new semiconductor liquid crystals with other liquid crystals are under
study in order to ascertain the possibility of their application in organic photovoltaic devices [8].
a)
b)
Fig. 1. Electrochromism in SmA phase (a) and electrofluorescence switching in the Colr phase (b).
References
[1] ]E. K. Fleischmann, R. Zentel, “Liquid crystalline order as a concept in materials science: from semiconductors to
stimuli-responsive devices”, Angew. Chem. Int. Ed., vol. 52, 8810-8827, 2013.
[2] M. O'Neill, S. M. Kelly, “Ordered materials for organic electronics and photonics”, Adv. Mater., vol. 23, 566-584,
2011.
[3] W. Pisula, M. Zorn, J. Y. Chang, K. Müllen, and R. Zentel, “Liquid crystalline ordering and charge transport in
semiconducting materials”, Macromol. Rapid Commun., vol. 30, 1179-1202, 2009.
[4] A. Beneduci, S. Cospito, A. Crispini, B. Gabriele, F. Nicoletta, L. Veltri, and G. Chidichimo, “Switching from
columnar to calamitic mesophases in a new class of rod-like thienoviologens”, J. Mater. Chem. C, vol. 1, 2233-2240,
2013.
[5] A. Beneduci, S. Cospito, B. C. De Simone, D. Imbardelli, G. Chidichimo, “Electrochromic switching in columnar
and calamitic thienoviologens”, in preparation.
[6] A. Beneduci, S. Cospito, M. La Deda, L. Veltri, and G. Chidichimo, “Electrofluorochromism in π-conjugated ionic
liquid crystals”, Nat. Commun., vol. 5, 3105, 2014.
[7] A. Beneduci, S. Cospito, R. Termine, G. Chidichimo, “Photoconduction and electronic charge carrier mobility in
liquid crystal thienoviologens”, in preparation.
[8] G. Chidichimo, A Beneduci, S. Cospito, V. Maltese, “Phase separation processes in liquid crystal donorsthienoviologen acceptor blends” in preparation.
Highly ordered smectic liquid crystals
for organic field effect transistors
Jun-ichi Hanna2, Hiroaki Iino, and Takayuki Usui
Imaging Science and Engineering Laboratory, Tokyo Institute of Technology,
226-8503, Nagatsuta, Midori-ku, Yokohama, Japan
e-mail: hanna@isl.titech.ac.jp
Liquid crystals are a self-organizing molecular semicondutor, which has a π-congugate
sysytem for a hopping site of charges and side chains along with the long molecular axis that help
self-organization of molecules, and exhibit charge carrier trasnport properties superior to those of
convential materials, e.g., amorphous organic semiconductors. Since the discovery of electronic
conduction in liquid crystals, various device applications have been proposed, including
photosensors, photoreceptors for copiers, light emitting diodes, solar cells, field effect trasnistors,
and so on. However, the device performances in these devices proposed are not as good as those
fabricated with conventional amorphous and crystalline organic semiconductors, which come from
a fact that basic elemental technologies have not been established to make the best use of the
properties of liquid crystals yet, leading to little attention to the liquid crystals in their industrial
applications of the devices.
We proposed application of polycrystalline thin films
of highly ordered semctic liquid crtystals solution-processed
for field effect transistors, in which we can utilize unique
properties of liquid crystals for overcoming the problems that
cannot be solved in non-liquidcrystalline materials, e.g.,
inhomogenuity and poor surface morphology in solutionprocessed polycrystalline thin fims and poor thermal durability
of the films in crystalline thin films. [1,2]. In fact, a FET
febricated with polycrystallinethin film of 2-phenyl-7decylbenzothienobenzothiophene (Ph-BTBT-10) exhibited
high thermal durability up to 200oC thanks to hghly ordered
smectic mesophase, in addition to a small variation of FET
performance thanks to unform and molecularly flat srrface
morphology of the films [3].
Recently we found that the FET mobility was
enhanced by about one-order of magnitute, up to 21.2 cm2/Vs
by thermal annealing at 120oC for 5 min. This high mobility is
comparable to thse in FET fabricated with an amorphous Figure 1. FET Mobility before and after
oxide semiconductor of InGaZnO, which indicates a high thermal annealing at 120oC for 5 min. in
bottom-gate and Top-contact FET
potential of liquid crystals in printed electronics.
fabricated with polycrystalline thin films
We discuss why organic transistor materials have to be a of Ph-BTBT-10 solution-processed, and
liquid crystal.
mobility variation in 22 FET devices.
References
[1] H. Iino and J. Hanna, Availability of Liquid Crystallinity in Solution Processing for Polycrystalline Thin Films, Adv.
Mater., 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim, Vol. 23, pp. 1748-1751, Feb. 2011.
[2] H. Iino, T. Kobori, and J. Hanna, Improved thermal stability in organic FET fabricated with a soluble BTBT
derivative, Journal of Non-Crystalline Solids, Elsevier, Vol. 358, pp. 2516–2519, Apr. 2012. Express, vol. 16, 9254–
9260, 2008.
[3] H. Iino, T,. Usui, and J. Hanna, submitted to Nature, 2014.
New composites based on liquid crystalline elastomers for microactuators and energy storage systems
Valentina Domenici1, Jerneja Milavec2, Blaz Zupancic2, Andraz Resetic2 and Bostjan Zalar2
1. Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via Risorgimento 35, 56126, Pisa, Italia
2. Department of Condensed Matter Physics, Jozef Stefan Institute, 39 Jamova Cesta, SI-1000, Ljubljana, Slovenia
e-mail: valentina.domenici@unipi.it
/LTXLG &U\VWDOOLQH (ODVWRPHUV /&(V DOVR NQRZQ DV ³DUWLILFLDO PXVFOHV´ RU ³VKDSH PHPRU\´
actuators can undergo controlled shape changes in response to external stimuli. Some well-known
examples include nematic polysiloxane-based LCE thin films, which contracts with increasing
temperature. This seminar will focus on recent advances on the preparation of new composite
materials in which LCE films change shape in response to the application of an external voltage or
controlled current.[1-4]
In particular, the chemical-physical characterization of these bilayer [1-4] and bi-components [5]
LCE-based systems will be reported and discussed, centering the discussion on new potential
applications as energy conversion and storage micro-systems and micro-actuators.
Figure 1. Optical microscopy images of gold-LCE bilayer system before (a,b,c) and after (d,e) actuation.
(f) SEM image of the same sample of image (e). Arrow indicates the nematic director orientation. [3]
References
[1] F. Greco, V. Domenici, A. Tareq, S. Romiti, V. Mattoli, ³%HQGLQJ $FWXDWLRQ RI D &RPSRVLWH /LTXLG &U\VWDO
(ODVWRPHUYLD'LUHFW-RXOH+HDWLQJ´, Fourth IEEE RAS/EMBS International Conference on Biomedical Robotics and
Biomechatronics, vol. 1, p. 645 ± 651, 2012.
[2] F. Greco, V. Domenici, S. Romiti, T. Assaf, B. =XSDQþLþ J. Milavec, B. Zalar, B. Mazzolai and V. Mattoli,
³Reversible Heat-Induced Microwrinkling of PEDOT:PSS Nanofilm Surface Over a Monodomain Liquid Crystal
Elastomer´, Mol. Cryst. Liq, Cryst. vol. 572, p. 40-49, 2013.
[3] B. Zupancic, B. Zalar, M. Remskar, V. Domenici, ³$FWXDWLRQRI*ROG-Coated Liquid &U\VWDO(ODVWRPHUV´, Applied
Physics Express, vol. 6, p. 21701 - 21701, 2013.
[4] F. Greco, V. Domenici, A. Desii, E. Sinibaldi, B. Zupancic, B. Zalar, B. Mazzolai, V. Mattoli, ³/LTXLG 6LQJOH
&U\VWDO(ODVWRPHU&RQGXFWLQJ3RO\PHUELOD\HUFRPSRVLWHDFWXDWRUPRGHOOLQJDQGH[SHULPHQWV´ Soft Matter, vol. 9,
p. 11405-11416, 2013.
[5] J. Milavec, A. Resetic, B. Zupancic, B. Zalar, V. Domenici, manuscript in preparation.
Acknowledgment: This research was partially supported by Centre of Excellence ³Namaste´ (Ljubljana ± Slovenia).
Structural Analyses of Liquid Crystal Blue Phases
Ying Wen 1, Yasushi Okumura2, Hiroki Higuchi2 and Hirotsugu Kikuchi 2
1. Department of Applied Science for Electronics and Materials, Kyushu University, Fukuoka, Japan
2. Institute for Material Chemistry and Engineering, Kyushu University, Fukuoka, Japan
e-mail:kikuchi@cm.kyushu-u.ac.jp
Choresteric blue phases (BPs) occur generally in a narrow temperature range between isotropic
phase and chiral nematic one. They have a self-assembled three-dimensional (3D) cubic lattice
consisting of double-twisted cylinders[1], and their lattice constant is a couple of hundred
nanometers. Physical properties of BPs such as the selective Bragg reflection in visible wavelength
region and fast electro-optical response are attributed to the unique cubic structure. Hence, a
detailed verification of the BP lattice models is worthwhile in the field of BP science. Here we
present a relationship between the lattice structure and the Bragg reflection wavelength of BP
studied by microspectroscope and confocal laser scanning microscopy (CLSM), which is a novel
imaging technique for obtaining high-resolution optical images in 3D scale.
A stripe pattern consisting of alternating bright and dark lines were found in a domain of multiorientation cell of BP with CLSM observation as shown in Figure 1(a). In addition to the periodicity
between the lines of the stripe, another periodicity along the stripe line was found through FFT of
the striped pattern. The length ratio of these two periodicities in the FFT image showed good
agreement with aspect ratio of periods in (211) plane in the BP model.
Considering the resolution of CLSM in the depth direction, the overlaid images of (211)
sections (Figure 1(b)) in different depths are expected to coincide with the observed stripe pattern.
Series of CLSM images of (211) plane with different depths, reflecting the internal structure of the
sample, were obtained by shifting the focal plane in every 25 nm in the direction of Z-axis. As a
result, relative brightness on the stripes with different brightness alternately changed as a function
of the depth. Through fitting with sine curves, the lattice constant was calculated to be about 330
nm according to the Z profile cycle of stripes. This result is identical with the lattice constants
obtained from 2D CLSM image of (211) and (111) plane and the reflection spectrum by
microspectroscope. Thus, the structure of (211) plane in 3D scale has been successfully confirmed.
Figure 1 (a) Stripe pattern image of BP I (211) plane observed by CLSM, (b) a corresponding overlapped image of crosssections of double-twisted cylinders on (211) plane in BP I lattice model.
References
[1] P. P. Crooker, “Chirality in Liquid Crystals”, Ed. by H. S. Kitzerow, C. Bahr, Springer, New York, pp. 186, 2001.
Active Plasmonics: Systems Design and Characterization
R. Caputo1, U. Cataldi1,2, L. De Sio3, T. Bürgi2 and C. Umeton1
1
Department of Physics and Centre of Excellence for the Study of Innovative Functional Materials University of
Calabria CNR-IPCF UOS Cosenza 87036 Arcavacata di Rende (CS), Italy
2
Department of Physical Chemistry, University of Geneva,
30 Quai Ernest-Ansermet, 1211 Geneva 4, Switzerland
3
Beam Engineering for Advanced Measurements Company, Winter Park, Florida 32789, USA
e-mail: roberto.caputo@fis.unical.it
The design and fabrication of samples showing plasmonic properties is fundamental for the
realization of devices exhibiting peculiar electromagnetic properties (e.g. Metamaterials) [1]. Much
curiosity is actually devoted to reconfigurable systems showing tunable plasmonic functionalities
(Fig. 1) [2-4]. Here we depict the scenario of actual and future possibilities offered by such systems
where the spectral position of the localized surface plasmon resonance (typical of metallic
nanoparticles) can be shifted through the application of external stimuli (e.g. electric field or
mechanical perturbation).
Figure 1. Basic principle of smart tapes (a) Sketch of the experimental setup. By stretching a PDMS sample coated with a single
layer of gold nanoparticles the average distance between them becomes larger in the stretching direction and shorter in the
perpendicular one. Stretching of the sample is accompanied by a remarkable change of colour from purple-red (b) to blue-violet (c).
Images were acquired with a polarizer, mounted to a camera, with direction of polarization perpendicular to the applied strain.
References
[1] V.G. Veselago, Sov. Phys. Usp. 10, 4, 509 (1968)
[2] L. De Sio, R. Caputo, U. Cataldi and C. Umeton, J. Mat. Chem., 21, 47, 18967 (2011)
[3] L. De Sio, A. Cunningham, V. Verrina, C.M. Tone, R. Caputo, T. Bürgi and C. Umeton, Nanoscale, 4, 7619 (2012)
[4] A.-L. Baudrion, A. Perron, A. Veltri, A. Bouhelier, P.-M. Adam and R. Bachelot, Nano Lett., 13, 1, 282 (2013)
Induction of Birefringence in Optically Isotropic Liquid Phase of
Chiral Mesogenic Compound
Isa Nishiyama1and Takahiro Yamamoto2
1. DIC Corporation, 4472-1 Oaza, Komuro, Ina-machi, Kita-Adachi-gun, Saitama 362-8577, JAPAN
2. Nanosystem Research Institute, National Institute of Advanced Industrial Science and Technology,
1-1-1, Higashi, Tsukuba 305-8565, JAPAN
e-mail: isa-nishiyama@ma.dic.co.jp
For common liquid crystal displays (LCDs), the precise control of the initial alignment of LC
molecules is needed so that a good dark state, thus a high contrast ratio, can be obtained. If the
optically isotropic LC phase is utilized, there is no need for concern about the initial alignment,
which is great advantage for the LCD production. Representative examples of such kinds of LC
phases are blue phases, which are optically isotropic without the application of electric field [1,2].
Another optically isotropic phase is a liquid phase which intrinsically shows no birefringence.
Therefore, if the birefringence can be induced in the liquid phase by the application of electric field
[3], it is of great use as a material for the LCD application. So far, one of our interests has been
focused on the evaluation of physical properties of dichiral azobenzene mesogenic compounds, in
which following interesting results have been obtained:
(a) Emergence of stable smectic Q (SmQ) phases [4],
(b) Photo-control of 3D structure of LC phases [5], and
(c) Chirality-driven cubic-tetragonal structural change [6].
In addition to those findings, the induction of the birefringence in the liquid phase has recently been
observed in a dichiral azobenzene ((S, S)-AZO-PB, Figure 1). The electrically-assisted increase in
the phase transition temperature is discussed in detail in terms of clinicity, and is compared with the
previously reported similar behaviours, including the shift of the ferroelectric-paraelectric phase
transition temperature by the application electric field observed in a ferroelectric LC [7].
(S, S)-AZO-PB
CH3 O
C6H13 C O C
H
∗
O
O C
N N
O
C O
O
CH3
C O C C6H13
H
Crystal 120 SmC*antiferroelectric 134 Isotropic Liquid
∗
Figure 1. Chemical structure and phase-transition temperatures of dichiral azobenzene liquid crystal used in this study.
References
[1] H. Kikuchi, “Liquid crystalline blue phases”, Struct. Bonding, vol. 128, p. 99, 2008.
[2] A. Yoshizawa, “Material design for blue phase liquid crystals and their electro-optical effects”, RSC Advances, vol.
3, p. 25475, 2013.
[3] I. Nishiyama, “Remarkable effect of pre-organization on the self assembly in chiral liquid crystals”, Chemical
Record, vol. 9, p. 340, 2010.
[4] T. Yamamoto, I. Nishiyama, and H. Yokoyama, “Novel photoinduced phase transition observed in threedimensional liquid-crystalline phase of azobenzene compound”, Chem. Lett., vol. 36, p. 1108, 2007.
[5] T. Yamamoto, I. Nishiyama, and H. Yokoyama, “Photo-control of chirality-induced liquid-crystalline 3D
structures”, Ferroelectrics, vol. 365, p. 39, 2008.
[6] T. Yamamoto, I. Nishiyama, M. Yoneya, and H. Yokoyama, “Novel chiral effect that produces the anisotropy in 3D
structured soft material: chirality-driven cubic-tetragonal liquid crystal phase transition”, J. Phys. Chem. B, vol. 113, p.
11564, 2009.
[7] K. Yoshino, K. Nakano, H. Taniguchi, and M. Ozaki, “Characteristic of dielectric behaviour of ferroelectric liquid
crystal at smectic-A and chiral smectic-C phase transition”, J. Phys. Soc. Jpn., vol. 56, p. 4150, 1987.
Multiple scale modelling and simulations of liquid crystals
Claudio Zannoni,
Dipartimento di Chimica Industriale “Toso Montanari”, Università,
viale Risorgimento, 4, 40136 Bologna, ITALY
e-mail: claudio.zannoni@unibo.it
Mesoscale models, based on the drastic simplification of representing molecules as simple rigid
objects such as spherocylinders or ellipsoids or even spins on a lattice have been the cornerstone of
the first generation of liquid crystal (LC) computer simulations (see, e.g.[1]),. While these approaches
are still very valuable in obtaining the general properties of complex LC, like LC Elastomers [2] one
of the most important current challenges is to relate a realistic molecular structure to physical
observables and predict properties such as morphologies, order parameters, and phase-transition
temperatures. This is essential, e.g. for applications in organic electronics, like organic solar cells [3]
and in interpreting detailed spectroscopic data. Atomistic scale molecular dynamics simulations can
now start to meet the challenge and we present some recent applications to nematic and smectic liquid
crystal systems [4,5] ] as well as to solutes in LC where we compare with detailed NMR data [6]. We
also tackle the problem of predicting alignment and anchoring strength of LC close to a solid
interface, considering in detail thin films of 5CB on crystalline (cristobalite) and amorphous silica
surfaces of increasing roughness [7].
[1] P. Pasini and C. Zannoni (Eds.), Advances in the Computer Simulations of Liquid Crystals (Kluwer,
Dordrecht , 2000)
[2] G. Skacej, C. Zannoni, Molecular simulations elucidate electric field actuation in swollen liquid
crystal elastomers, PNAS, 109, 10193–10198 (2012)
[3] J. Idé, R. Méreau, L. Ducasse , F. Castet, H. Bock, Y. Olivier, J. Cornil, D. Beljonne, G. D’Avino,
O. M. Roscioni, L.Muccioli, C. Zannoni, Charge dissociation at interfaces between discotic liquid
crystals: the surprising role of column mismatch, J.Am. Chem.Soc., 136, 2911 (2014)
[4] M.F. Palermo, A.Pizzirusso, L.Muccioli, C.Zannoni, An atomistic description of the nematic and
smectic phases of 4-n-octyl-4'cyanobiphenyl (8CB), J.Chem.Phys., 138, 204901 (2013)
[5] Y. Olivier, L. Muccioli, C. Zannoni, Quinquephenyl: the simplest rigid rod-like nematic liquid
crystal. Or is it? An atomistic simulation, ChemPhysChem, DOI: 10.1002/cphc.201301126 (2014)
[6] A. Pizzirusso, M. E. Di Pietro, G. De Luca, G. Celebre, M. Longeri, L. Muccioli, C. Zannoni,
Order and conformation of biphenyl in cyanobiphenyl liquid crystals. A combined atomistic molecular
dynamics and 1H-NMR study, ChemPhysChem, DOI:10.1002/cphc.201400082 (2014).
[7] O. M. Roscioni, L. Muccioli, R. G. Della Valle, A. Pizzirusso, M. Ricci, C. Zannoni, Langmuir,
29, 8950 (2013). G
Heat-driven unidirectional rotation of cholesteric LC droplets
Jun Yoshioka, Fumiya Ito, Yuto Suzuki, Hideaki Takizawa and Yuka TABE*
Department of Pure & Applied Physics, Graduate School of Advanced Science & Engineering, Waseda University
3-4-1 Okubo, Shinjuku, Tokyo, Japan
*e-mail: tabe@waseda.jp
When a chiral liquid crystal is given a transport current, a
unidirectional molecular rotation is known to take place[1,2],
which is called Lehmann effect. In this report, we study the heatcurrent driven molecular dynamics in two-types of hemispherical
cholesteric droplets by means of optical microscopies[3]. Both the
droplets, coexisting with the isotropic phase and contacting on a
glass substrate, are characterized by the convex-concave modulated
surface and the inside orientational helix. The difference between
them is the helical axis direction, i.e., one is perpendicular and the
other is parallel to the substrate. Under the temperature gradient
perpendicular to the substrate, the droplet whose helical axis is
parallel to the heat current exhibited the pure director rotation,
while the one with the axis perpendicular to the heat flow rotated
by themselves as a rigid body. In the two droplets, the rotational
conversion efficiency from the temperature gradient into the
angular velocity showed very different dependence on the chirality
strength and on the droplets size, suggesting that the rotations of
the two droplets may be driven by the independent torques with
different origins. This is the first observation that the cholesteric
droplets under the temperature gradient exhibit the two rotational
modes, the pure director rotation and the molecular barycentric
motion, which can be switched to each other by changing the
heat-current direction between parallel and perpendicular to the
helical axis.
0 sec
10 !m
10 sec
20 sec
30 sec
Figure 1: Two types of cholesteric droplets
under the heat current directed into the
paper. The helical axes of the left and the
right droplets are perpendicular and parallel
to the paper, respectively.
References
[1] O. Lehmann, Ann. Phys. 2, 649, 1900.
[2] P. Oswald and A. Dequidt, Europhys. Lett. 83, 16005, 2008.
[3] J. Yoshioka, F. Ito, Y. Suzuki, H. Takahashi, H. Takizawa and Y. Tabe, Soft Matter in press.
Acknowledgment: Effort sponsored by the NEXT program of Japan Society for the Promotion of Science.
Halogen-bonded Liquid Crystals, Gels, and Polymers
Pierangelo Metrangolo1,2*, Gabriella Cavallo1, Arri Priimagi1,3, Giuseppe Resnati1, Giancarlo
Terraneo1
1. Laboratory of Nanostructured Fluorinated Materials (NFMLab), Department of Chemistry, Materials,
DQG&KHPLFDO(QJLQHHULQJ³*LXOLR1DWWD´3ROLWHFQLFRGL0LODQR9LD/0DQFLQHOOL0LODQR,WDO\
2. Unit BA3134 Chemical Synthesis and Polymerisation Technologies, VTT Technical Research Centre of
Finland, VTT FI-02044, Finland
3. Department of Applied Physics, Aalto University, Aalto FI-00076, Finland
e-mail: pierangelo.metrangolo@polimi.it
According to the IUPAC, a halogen bond (XB) occurs when there is evidence of a net attractive
interaction between an electrophilic region associated with a halogen atom in a molecular entity and
a nucleophilic region in another, or the same, molecular entity.1
Similarities between halogen and hydrogen bonds have been emphasized in several contexts.
However, it is the differences between these interactions that provide with an extra value for the
design and construction of XB-based supramolecular materials.2 For example, the directionality of
XB has provided with unique design tools for preparing photoresponsive, liquid-crystalline
complexes from non-liquid-crystalline constituents, with truly unique optical performances.3
Moreover, we have employed the tunable interaction strength of halogen bonding to gain
fundamental understanding of light-induced mass migration in photoswitchable polymerazobenzene complexes; namely not many other noncovalent interactions allow controlling the
polymer-chromophore interaction strength without altering the electronic properties of the
chromophore.4 The use of halogen-bonded mesogens to control hierarchical polymer self-assembly
over the mm length scale,5 together with our recent work on halogen-bond-triggered supramolecular
gelation,6 open up new avenues in the design of supramolecular systems.
Figure 1. Halogen-bonded dimer between a pyridyl derivative (right) and a halogen bond-donor molecule (left) containing
a photoswitchable azo group.
References
[1] G. R. Desiraju, P. S. Ho, L. Kloo, A. C. Legon, R. Marquardt, P. Metrangolo, P. A. Politzer, G. Resnati, and K.
Rissanen, ³Definition of the halogen bond´ Pure Appl. Chem., vol. 85, 1711 ± 1713, 2013.
[2] A. Priimagi, G. Cavallo, P. Metrangolo, and G. Resnati, ³The Halogen Bond in the Design of Functional
6XSUDPROHFXODU0DWHULDOV5HFHQW$GYDQFHV´Acc. Chem. Res., vol. 46, 2686±2695, 2013.
[3] A. Priimagi, M. Saccone, G. Cavallo, A. Shishido, T. Pilati, P. Metrangolo, and G. Resnati, ³3KRWRDOLJQPHQWDQG
Surface-Relief-Grating Formation are Efficiently Combined in Low-Molecular-Weight Halogen-%RQGHG&RPSOH[HV´
Adv. Mater., vol. 24, OP345-352, 2012.
[4] A. Priimagi, G. Cavallo, A. Forni, M. Gorynsztejn-Leben, M. Kaivola, P. Metrangolo, R. Milani, A. Shishido, T.
Pilati, G. Resnati, and G. Terraneo, ³Photoresponsive Supramolecular Polymers: Halogen Bonding versus Hydrogen
Bonding in Driving Self-Assembly and Performance of Light-Responsive Supramolecular Polymers´ Adv. Funct.
Mater., vol. 22, 2572-2579, 2012.
[5] N. Houbenov, R. Milani, M. Poutanen, J. Haataja, V. Dichiarante, J. Sainio, J. Ruokolainen, G. Resnati, P.
Metrangolo, and O. Ikkala, Nat. Commun., 2014, in press.
[6] L. Meazza, J. A. Foster, K. Fucke, P. Metrangolo, G. Resnati, and J. W. Steed, ³Halogen-bonding-triggered
supramolecular JHOIRUPDWLRQ´, Nat. Chem., vol. 5, 42-47, 2013.
Second Order Phase Transition
in Hyper Swollen Lyotropic Liquid Crystals
Jun Yamamoto1, HyeRan Jo2, Yoichi Takanishi1, Giusy Scalia2, Jan Lagerwall2
1. Department of Physics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan,
2. Graduate School of Convergence Science and Technology, Seoul National University, Suwon 443-270, Korea,
We have investigated the phase transition behavior by DLS measurement in the hyperswollen lyotropic nematic (LN) phase, formed by a combination of anionic and cationic surfactants
(sodium dodecyl sulfate; SDS and dodecyl trimethyl ammonium bromide; C12TAB, respectively)
at a total surfactant concentration ! ! 8wt%. The mole fraction " between SDS and C12TAB is
varied between 2.3 and 2.7. We have found an interesting type of continuous 2nd order isotropicnematic (I-N) phase transition for some surfactant ratios, and investigating the driving mechanism.
Director fluctuations observed in depolarized (vertical-to-horizontal polarization rotation; VH)
signal, clearly shows critical slowing down on both sides of the phase transition as shown in Figure.
It should be noted that in all samples which show the 2nd order I-N phase transition, the size of
micelles is drastically reduced above the phase transition. In addition, all have the same radius of
the micelle, almost equivalent to the length of the surfactant molecules, which can be estimated
from translational diffusion constant observed in polarized (vertical-to-vertical polarization rotation;
VV) scattering with Einstein-Stokes’s law. It is quite reasonable that the micelle shape becomes
spherical in the isotropic phase. We concluded that the 2nd order transition is driven by the decrease
in the anisotropy of “building blocks” of the nematic, namely the rod to sphere transition of
micelles. The birefringence continuously weakens near the 2nd order I-N phase transition due to the
decrease in order parameter as well as in the simultaneous decrease in anisotropy of the building
blocks. The latter also strongly affects the excluded volume interaction between micelles and thus
the origin of orientational order. We have found a 2nd order I-N phase transition driven by the
shape transformation of the building blocks for the first time.
Figure 1 Temperature dependence of relaxation time for two types of fluctuations with the prediction of their respective dispersion
relations (!=8wt%, "=2.55).
Photopyroelectric calorimetry for the thermal and optical evaluations of
og light
induced transitions in liquid crystals .
U. Zammit, F. Mercuri, S. Paoloni, M. Marinelli
Dipartimento di Ingegneria Industriale, Università di Roma ‘‘Tor Vergata’’, Via del Politecnico
1, 00133 Roma, Italy
e-mail: zammit@uniroma2.it
In this study, the photopyroelectric calorimetry has been employed for the simultaneous
determination of thermal conductivity k, and the specific heat c over a temperature range including
both the Smectic-Nematic and Nematic-Isotropic phase transitions temperature, before, during and
after the UV light exposure. As expected, the UV light causes both the transition temperatures to
shift to larger values due to the photochromic molecules switching to their more ordered open
configuration. This reduces their disordering power on the LC mean molecular field with respect to
that caused when they are in their closed configuration. As reported in fig. 1, as the UV light is
turned off, the transition temperatures do not return down to the corresponding values obtained
before the light had been switched on. This indicates that the prolonged (several hours) exposure of
the photochromic molecules to the UV light, causes the switching to their open form to become
irreversible, unlike the previously reported reversible switching effects following short exposure
(several seconds) to UV light. The thermal conductivity studies revealed that, upon entering the
smectic phase when cooling the sample with the UV light on, the homeotropic alignment of the LC
molecules in the nematic phase may get disrupted, giving rise to multi-domain focal conics textures.
2,8
c (J/gK)
SA
N
I
2,4
2,0
28
30
32
34
36
38
40
T (°C)
Figure 1. Specific heat over smectic - nematic and nematic - isotropic phase transitions in 8CB liquid crystals with 2% mass fraction
of naphtopyran photochromic molecules molecules: before (dark gray) , during (black) and after (light gray) UV light illumination.
Dynamic Amplification of Optical Signals in Photorefractive
Ferroelectric Liquid Crystals
Takeo Sasaki and Yumiko Naka
Department of Chemistry, Faculty of Science, Tokyo University of Science,
1-3 Kagurazaka, Shinjuku-ku Tokyo 162-8601
e-mail: sasaki@rs.kagu.tus.ac.jp
1. Introduction
The photorefractive effect is a phenomenon
N
CH
OC H
8PP10
wherein a change in the refractive index is induced
N
N
by a combined mechanism of photovoltaic and
CH
OC H
8PP8
base LC
N
electro-optic effects. The interference of two laser
N
CH
OC H
beams in a photorefractive material establishes a
8PP6
N
refractive index grating (holograms). The
O
photorefractive
effect
in
surface-stabilized
S
S
*
CH
O
S
Photoconductive
ferroelectric liquid crystals (SS-FLCs) doped with
chiral dopant
3T-2MB
a photoconductive compound has been reported
NO
[1]. When laser beams are interfered in a
NO
O N
Sensitizer / electron trap
photoconductive SS-FLC, an electric field is
TNF
O
induced within the LC phase and the direction of Fig. 1. Photorefractive FLC mixture containing ternary
the spontaneous polarization is changed giving rise mixture of smectic LCs.
to a change in refractive index of the corresponding
area. In this study, chiral compounds that also show
photoconductivity were synthesized and mixed
with the base LC compounds (Fig. 1). The
properties of the obtained photoconductive FLC
mixtures were examined and the relationship
between the photorefractive effect and properties of
the FLC mixtures were investigated.
2. Results and discussions
The photorefractive effect of FLC was evaluated Fig. 2. Optical image amplification experiment.
by two-beam coupling experiment. A gain A computer-generated animation was displayed on the SLM. The
modulated the object beam (488 nm), which was irradiated
coefficient higher than 1200 cm-1 was obtained SLM
on the FLC sample and interfered with the reference beam. The
with the application of only 1 V/µm. This value is Image transmitted through the FLC sample was monitored by
CCD camera.
seven times larger than the gain coefficients
reported in other photorefractive FLCs. The grating formation time decreased with increasing
electric field strength due to the increased efficiency of charge generation. The shortest formation
time was obtained to be 1 ms at 1 V/µm external electric field. Optical image amplification was
demonstrated. A computer-generated animation was displayed on the SLM. The frame rate was 30
fps. A 473 nm beam was irradiated on the SLM and the reflected beam was incident on the FLC
sample. A pump beam interfered with the beam from the SLM in the FLC sample. A laser beam
containing the moving image of the animation was amplified by the incident pump beam (Fig. 2).
This result shows that the response of the photorefractive FLC was fast enough to amplify the
optical image in real time.
8 17
10 21
8 17
8 17
8 17
6 13
8 17
2
2
2
Reference
[1] T. Sasaki, M. Ikegami, T. Abe, D. Miyazaki, S. Kajikawa, Y. Naka, “Real-time dynamic hologram in
photorefractive ferroelectric liquid crystal with two-beam coupling gain coefficient of over 800 cm-1 and response time
of 8 ms” Appl. Phys. Lett., 102, 063306, 1-4 (2013).
High-HTP macrocyclized pheynyl cinnamate dimer utilizable as
photo-responsive chiral dopant for nematic liquid crystals
M.Tokita, M. Ito, K. Marumo, Y. Harada, S. Kang, K. Sakajiri, and J. Watanabe
Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo 152-8552, Japa
Twin dimers forming liquid crystals (LCs) are composed of two mesogenic units
linked by a flexible alkyl spacer. These linear dimers having two alkyl tails can be
cyclized by ring-closing metathesis under high dilation in the presence of the first
Grubbs catalyst. Macrocyclization of twin dimers forces the spacer to fold and the two
mesogens to face to each other at a short distance and restricts the conformations.[1]
When the spacer has a chiral carbon, two mesogens are fixed in a skewed overlapping
alignment with the handedness determined by the spacer’s chirality. Such a cyclic chiral
dimer exhibited the helical twisting power in the nematic LC solvent four times higher
than that of the precursor linear dimmer and twenty times higher than that of
monomeric compound.[2]
Here, macrocyclized phenyl cinnamate dimer with a chiral spacer was prepared and
its photochemistry was compared with that of the precursor linear dimer and basic
monomer. Irradiation of cyclic and linear dimers induced intra-molecular [2+2]
photodimerization of cinnamate groups though that of monomer resulted merely in
cis-trans isomerization of cinnamate. [3–9] The rate of photodimerization in the cyclic
dimer was 20 times larger than that in linear one. With this photodimerization, the cyclic
dimer decreased helical twisting power (HTP) from 27.5 µm−1 to 6.7 µm−1. We
demonstrated that such a macro-cyclized dimer can be a photo-responsive chiral dopant
of chiral nematic liquid crystals which will be applied for some interesting fields.
1.
2.
M. Itoh, J. Watanabe, et al., Liq. Cryst. 2009, 36, 1443–1450.
M. Itoh, J. Watanabe, et al., J. Mater. Chem. 2011, 21, 1697–1699; Liq. Cryst., 2013,
40, 339-344; Liq. Cryst., 2013, 40, 900-905.
3.
4.
5.
P. Keller, Chem. Mat. 1990, 2, 3–4.
L. -C. Chien and L. G. Cada, Macromolecules 1994, 27, 3721–3726.
N. Kawatsuki, C. Suehiro, T. Yamamoto, Macromolecules 1998, 31, 5984–5990.
6.
7.
8.
N. Kawatsuki, et al., Macromolecules 2000, 33, 1698–1702.
N. Kawatsuki, et al., Macromolecules 2002, 35, 706–713.
B. Sapich, et al., Macromolecules 2001, 34, 5694–5701.
9.
R. Ishige, , J. Watanabe, et al., Macromolecules, 2008, 41, 2671-2676.
Molecular geometry, elastic constants and twist-bend nematic phase
Cristina Greco,1 Geoffrey R. Luckhurst,2 and Alberta Ferrarini 1
1. Department of Chemical Sciences, University of Padova, via Marzolo 1, I-35131 Padova, Italy
2. School of Chemistry, University of Southampton, Highfield, Southampton SO17 1BJ, United Kingdom
alberta.ferrarini@unipd.it
Recently, the observation of a number of unusual features in the second nematic phase formed by
bent-shaped liquid crystal dimers, lead to the identification of a novel nematic organization, which
following a prediction by Dozov was called a Twist-Bend Nematic (NTB).[1,2] This is characterized
by a periodically distorted director forming a conical helix with a doubly degenerate handedness.[2]
Such a picture was confirmed by a variety of experimental techniques, but agreement on this phase
structure is not universal. However, valuable insights have been reached by transmission electron
and optical microscopy[3,4] as well as electro-optical measurements.[5] From these and the analysis
of NMR experiments,[6,7] a remarkably short periodicity, of the order of a few molecular lengths,
could be identified.
Although the structural features of the NTB phase are becoming clear, the mechanism of the
NTB-N transition, the role of the dimer structure and the connection with the elastic properties [8,9]
remain open questions. However, low values of the bend elastic constant seem to be important.
Here, using a molecular field approach, we can provide a consistent picture of the phase transition
and the elastic behaviour, in relation to the molecular geometry. In particular, theory allows us to
analyse the results of different experiments, focussing on those features that have been taken as a
signature of the NTB organization.
References
[1] M. Cestari, S. Diez-Berart, D. A. Dunmur, A. Ferrarini, M. R. de la Fuente, D. J. B. Jackson, D. O. Lopez, G. R. Luckhurst,
M. A. Perez-Jubindo, R. M. Richardson, J. Salud, B. A. Timimi, and H. Zimmermann, “Phase behaviour and properties of the
liquid-crystal dimer 1”,7”-bis(4-cyanobiphenyl-4’-yl)heptane: a twist-bend nematic liquid crystal”, Phys. Rev. E 84, 031704,
2011.
[2] I. Dozov, “On the spontaneous symmetry breaking in the mesophases of achiral banana-shaped molecules”, Europhys. Lett.
56, 247-253, 2001.
[3] D. Chen, J. H. Porada, J. B. Hooper, A. Klittnick, Y. Shen, M. R. Tuchband, E. Korblova, D. Bedrov, D. M. Walba, M. A.
Glaser, J. E. Maclennan and N. A. Clark, “Chiral heliconical ground state of nanoscale pitch in a nematic liquid crystal of
achiral molecular dimers”, PNAS 110, 15931-15936, 2013.
[4] V. Borsch, Y.-K. Kim, J. Xiang, M. Gao, A. Jakli, V. P. Panov, J. K. Vij, C. T. Imrie, M. G. Tamba, G. H. Mehl, and O. D.
Lavrentovich, “Nematic twist-bend phase with nanoscale modulation of molecular orientation”, Nat. Commun. 4, 2635, 2013.
[5] C. Meyer, G.R. Luckhurst, and I. Dozov, “Flexoelectrically driven electroclinic effect in the twist-bend nematic phase of
achiral molecules with bent shapes”, Phys. Rev. Lett. 111, 067801, 2013.
[6] L. Beguin, J.W. Emsley, M. Lelli, A. Lesage, G.R. Luckhurst, B.A. Timimi, and H. Zimmermann, “The chirality of a twistbend nematic phase identified by NMR spectroscopy”, J. Phys. Chem. B 116, 7940-7951, 2012.
[7] C. Greco, G. R. Luckhurst, and A. Ferrarini, “Enantiotopic discrimination and director organization in the twiste-bend
nematic phase”, Phys. Chem. Chem. Phys 15, 14961-14965, 2013.
[8] S. M. S. Shamid, S. Dhakal, and J. V. Selinger, “Statistical mechanics of bend flexoelectricity and the twist-bend
phase in bent-core liquid crystals”, Phys. Rev. E 87, 052503, 2013.
[9] E. Virga, “Elasticity of Twist-Bend Nematic Phases”, arXiv:1403.0119v2.
Structure-sensitive bend elastic constants between pN and sub-nN
S. Aya,1 H. Obara,2 K. Okano,2 T. Yamashita,2 D. Pochiecha,3 E. Gorecka,3 N. Vaupotic,4
F. Araoka,1 K. Ishikawa,1 and H. Takezoe1
1. Department of Organic and Polymeric Materials, Tokyo Institute of Technology, O-okayama, Meguro, Tokyo, 1528552, Japan
2. Department of Pure and Applied Chemistry, Tokyo University of Science, 2641 Yamazaki, Noda-shi, Chiba, 2788510, Japan
3. Department of Chemistry, University of Warsaw, ul. !wirki i Wigury 101, 02-089 Warsaw, Poland
4. Faculty of Natural Sciences and Mathematics, Institute of Physics, University of Maribor, Koroska, 160, 2000
Maribor, Slovenia
e-mail: takezoe.h.aa@m.titech.ac.jp
Elasticity is an important factor for the performance of liquid crystal (LC) devices. It is known
that the curvature elastic constants in calamitic nematic (N) LC molecules, K22, K11, and K33 are
usually in the range of pN in ascending order of magnitude. In this study, we synthesized
diphenylacetylene-core-based compounds and found that K33 varies sensitively depending on the
chemical structure (Fig. 1); one of the compounds (p-oxyAzo5) has surprisingly high elastic
constants against bend deformation, a sub-nN, over a wide temperature range; about 100 times
larger than that in general liquid crystals [1]. In contrast, p-oxyEster5 has K33 of normal values (pN)
and K33 of p-oxyTolane5 is in between.
To clarify the origin of the unusually huge K33 values, we measured x-ray diffraction in their N
phase and found a cybotactic smectic cluster formation in whole the N range only in p-oxyAzo5 [1].
Then, why can p-oxyAzo(n) homologues stabilize cybotactic clusters exceptionally? To address this,
we performed ab initio molecular orbital theory calculations for core structures of molecules used,
by which we search single molecular most-stable structure. The relative potential energy of the core
part of studied molecules was calculated as a function of dihedral angle of a phenyl ring, as shown
in Fig.2. In the figure, angles 0 and 180 degrees correspond to parallel orientation of two phenyls.
We found remarkable differences in four analogous compounds; Only the azo group imposes their
molecules into flat geometry with a high potential barrier. We may expect p-oxyAzo5 can pack
quite well into smectic-like structure as we confirmed in the experimental results.
Figure 1. K33 as a function of temperature
in three compounds.
Figure 2. Energies as a function of dihedral angle
in four compounds.
References
[1] S. Aya, H. Obara, D. Pociecha, F. Araoka, K. Okano, K. Ishikawa, E. Gorecka, T. Yamashita, and H. Takezoe,
“Highly elastic liquid crystal with bend elastic constant of sub-nN mediated by the resident molecular assemblies”, Adv.
Mater.vol. 26, p. 1918, 2014.
LCDiXRay:
A User-Friendly Program for the Indexation of Columnar Liquid Crystals PXRD Patterns
Nicolas Godbert 1, Alessandra Crispini 1, Mauro Ghedini 1, Manuela Carini 2, Francesco
Chiaravalloti 3 and Andrea Ferrise 4
1. Mat-inLab, LASCAMM CR-INSTM della Calabria, Dipartimento di Chimica e Tecnologie Chimiche, Università
della Calabria, 87036 Arcavacata di Rende (CS), ITALY
2. Dipartimento di Ingegneria per l’Ambiente ed il Territorio e Ingegneria Chimica, Università della Calabria, 87036
Arcavacata di Rende (CS), ITALY
3. Dipartimento di Fisica, Università della Calabria, 87036 Arcavacata di Rende (CS), ITALY
4. Dipartimento di Informatica, Modellistica, Elettronica e Sistemistica, Università della Calabria, 87036 Arcavacata
di Rende (CS), ITALY
e-mail: Nicolas.godbert@unical.it
Within the present contribution LCDiXRay,[1] our newly developed standard computerized procedure for the
indexation of X-Ray Powder Diffraction (PXRD) patterns of columnar liquid crystals, will be described. This
user-friendly software implemented in an objected-oriented framework has been included in a Java GUI
program. LCDixRay allows the straightforward identification of the columnar liquid-crystal mesophase
symmetry - Hexagonal (Colh), Rectangular (Colr), or Oblique (Colo) as well as the determination of all
structural information extracted from a properly indexed PXRD spectrum. In particular, the proposed program
notably accelerates the identification of columnar mesophases together with the in situ determination of their
structural parameters such as: mesophase type, cell dimension, cross section area, intermolecular stacking
distance between consecutive discoids, and in the case of ordered mesophases, the estimation of the
number of molecules constituting each discoid. Through chosen examples, the performances of LCDiXRay
will be illustrated.
Figure 1. LCDiXRay.
References
[1] N. Godbert, A. Crispini, M. Ghedini, M. Carini, F. Chiaravalloti, and A. Ferrise, “LCDiXRay: a user-friendly
program for powder diffraction indexing of columnar liquid crystals”, J. Appl. Cyrst., vol. 47, p. 668-679, 2014.
Note: LCDiXRay is freely available upon request (nicolas.godbert@unical.it)
Acknowledgment: Effort sponsored by the European Community’s Seventh Framework Programme (FP7 2007-2013),
through the MATERIA project (PONa3_00370).
Comparison of Molecular Orientation Structure of Photoalignable Liquid
Crystalline Polymer Films at the Near-surface and in Bulk
Nobuhiro Kawatsuki 1, Mizuho Kondo 1, Yu-ichi Haruyama 2, Shinji Matsui 2
1. Department of Materials Science and Chemistry, Graduate School of Engineering, University of Hyogo, 2167
Shosha, Himeji, Hyogo 671-2280, Japan
2. Laboratory of Advanced Science and Technology for Industry, University of Hyogo, 3-1-2 Koto, Kamigori, Ako,
Hyogo 678-1205 Japan
e-mail:kawatuki@eng.u-hyogo.ac.jp
Photoalignment of liquid crystals (LCs) has received considerable attention in display industries
due to its cleanness and patternability. [1] We have been carrying out systematic studies on
photoresponsive liquid crystalline polymeric materials that show photoinduced molecular
reorientation (Fig. 1a), and demonstrated their application to birefringent films, polarization
holography and LC photoalignment layers. [2] One of the features of our materials is that the LC
photoalignment can be achieved with large azimuthal anchoring, which is important for in-plane
switching LC displays. For example, a LC polymer film with photo-crosslinkable mesogenic side
groups exhibits significant molecular orientation parallel to the polarization of linearly polarized
(LP) UV light and reveals large azimuthal LC anchoring when the film is exposed to LPUV light
and subsequently annealed. [3]
For the LC alignment, evaluation of the near-surface structure of the alignment layer is
important to investigate the interaction between LC molecules and the film. In this paper, thermally
stimulated photoinduced molecular reorientation structures of photoreactive liquid crystalline
polymer films at the near-surface and in bulk are clarified using near-edge X-ray absorption fine
structure (NEXAFS) and polarization UV absorption spectroscopies, respectively [4]. NEXAFS
shows an effective uniaxial in-plane orientation at the near-surface in films thicker than 40 nm, but
the orientation performance in bulk decreases when film thickness decreases. Additionally, oblique
molecular reorientation behavior both at the near-surface and in bulk is presented as functions of
film thickness and exposure angles.
Figure 1. (a) Schematic illustration of photoinduced orientation mechanism and (b) detailed molecular orientation structure of
photoalignable LCP film.
References
[1] V. G. Chigrinov, V. M. Kozenkov, H.-S. Kwok, Photoalignment of Liquid Crystalline Materials, John Wiley &
Sons, West Sussex, England, (2008).
[2] N. Kawatsuki Chem. Lett. 40, 548-554 (2011), T. Seki, N. Kawatsuki, M. Kondo, Photoresponsive, Photosensitive
and Photoalignable Materials in Handbook of Liquid Crystals (J. W. Goodby, P. J. Collings, T. Kato, C. Tschierske, H.
F. Gleeson, P. Raynes eds), Vol. 8: 8, Applications of Liquid Crystals, chapter 18, pp. 539-579, Wiley-VCH (2014).
[3] N. Kawatsuki, K. Goto, T. Kawakami, T. Yamamoto Macromolecules 35, 706-713 (2002), N. Kawatsuki, K.
Hamamo, H. Ono, T. Sasaki, K. Goto, Jpn. J. Appl. Phys. 46, 339-341 (2007)
[4] N. Kawatsuki, Y. Inada, M. Kondo, Y. Haruyama, S. Matsui Macromolecules 47, 2080-2087 (2014)
Liquid crystal channel waveguides for optofluidic applications
Rita Asquini
Luca Martini, Antonio d'Alessandro
Department of Information Engineering, Electronics and Telecommunications,
Sapienza university of Rome via Eudossiana, 18 - 00184 Rome - Italy
e-mail: rita.asquini@uniroma1.it
The research on the integration of optics and microfluidics, better known as optofluidics, in
combination with the optical properties of liquid crystals (LC) can be used to make both electrically
and optically controlled cores for switchable and reconfigurable waveguides [1-2]. Several different
devices were designed, simulated, developed and characterized, achieving routing capabilities in LC
waveguides with electro-optical [3-6] and all-optical [7] control, and through nematicon
propagation [8].
In this paper we present our recent results on light propagation in polydimethylsiloxane (PDMS)
channels with LC infiltrated core. Polarization independent light transmission was observed, despite
the typical LC optical anisotropy, and we measured a transmission variation due to the orientation
of the LC molecules of only 0.3 dB. The experimental results were found to be consistent with both
the orientation observed under a polarizing microscope and the simulations. Polarization insensitive
behavior is an interesting feature which makes the proposed LC waveguides a basic structure for
low cost devices, which can be used for optical interconnections or integrated with microfluidic
circuits for lab on chip and sensing applications.
References
[1] R. Asquini and A. d'Alessandro, "All-Optical Switching and Filtering Based on Liquid Crystals and
Photosensitive Composite Organic Materials ", Mol. Cryst. Liq. Cryst., vol. 572, no. 1, pp. 13-23, 2013.
[2] D. C. Zografopoulos , R. Asquini, E. E. Kriezis, A. d'Alessandro, and R. Beccherelli, "Guided-wave
liquid-crystal photonics", Lab Chip, vol. 12, pp. 3598-3610, 2012.
[3] R. Asquini, A. Fratalocchi, A. d’Alessandro, and G. Assanto, “Electro-optic routing in a nematic liquidcrystal waveguide”, Applied Optics, vol. 44, no. 19, pp. 4136-4143, 2005.
[4] A. d’Alessandro, B. Bellini, D. Donisi, R. Beccherelli and R. Asquini, “Nematic liquid crystal optical
channel waveguides on silicon”, IEEE J. Quantum Electron., vol. 42, no. 10, pp. 1084-1090, 2006.
[5] R. Asquini, D. Donisi, M. Trotta, A. d’Alessandro, B. Bellini, G. Gilardi, R. Beccherelli, “Realization of
a liquid crystal electrically controlled optical waveguide on micromachined silicon”, Mol. Cryst. Liq. Cryst.,
vol. 500, pp. 23-30, 2009.
[6] D. Donisi, B. Bellini, R. Beccherelli, R. Asquini, G. Gilardi, M. Trotta, and A. d’Alessandro, “A
switchable liquid-crystal optical channel waveguide on silicon”, IEEE J. Quantum Electron., vol. 46, no. 5,
pp. 762-768, 2010.
[7] A. d’Alessandro, R. Asquini, M. Trotta, G. Gilardi, R. Beccherelli, I. C. Khoo, "All-optical intensity
modulation of near infrared light in a liquid crystal channel waveguide", Appl. Phys. Lett., vol. 97, no. 9, pp.
093302(1)- 093302(3), 2010.
[8] A. Piccardi, M. Trotta, M. Kwasny, A. Alberucci, R. Asquini, M. Karpierz, A. d’Alessandro, G. Assanto,
"Trends and trade-offs in nematicon propagation", Appl. Phys. B: Lasers and Optics, vol. 104, no. 4, pp. 80581, 2011.
Phase Structure and Transition Mechanism in AzobenzeneContaining Bicontinuous Cubic Liquid Crystalline Systems.
Shoichi Kutsumizu, Ryo Hori, and Yohei Miwa
Department of Chemistry and Biomolecular Science, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan
e-mail: kutsu@gifu-u.ac.jp
Liquid crystals (LCs) are a kind of liquid the structure of which can easily respond to external
stimuli such as electric field or deformation. Bicontinuous cubic (Cubbi) phases are such LCs but
possess much complicated molecular organizations, 3D network structures with cubic symmetry,
which was first reported by Luzzati more than 30 years ago [1]. Based on the characteristic
structures, many applications have been proposed such as catalytic bases, separation membranes,
3D conductors, etc. [2]. In thermotropic systems, the Cubbi LCs are in temperature scale neighbored
by other LCs, mostly 1D smectic C (SmC) LC. Reflecting the different dimensionality of ordering
(3D vs 1D), the two show quite different physical properties (e.g., optically isotropic and viscous in
Cubbi vs optically anisotropic and relatively fluid in SmC). Our research group focused on the
dynamic nature of those structures as LCs and selected UV light as external stimulus. By means of
photoisomerization of a doped azobenzene derivative, we have achieved the light-driven SmC to
Cubbi phase transition [3].
The systems constructed were binary mixtures of
4-n-docosyloxy-3-nitrobiphenyl-4-carboxylic acid
(ANBC-22, in which “22” indicates the number of
carbon atoms in the alkyl tail) and ethyl 4-(4-ndocosyloxyphenylazo)benzoate
(AZO-22).
A
mixture containing 20 mol% AZO-22 shows an
enantiotropic
transition
behavior
of
crystalSmCIa3d-CubbiIm3m-CubbiIsotropic
liquid. When the SmC phase is irradiated with UV
Figure 1. Schematic description for light-driven SmC−
light (=365 nm) at a temperature far below the Ia3d
Cubbi phase transitions.
SmCIa3d-Cubbi phase transition temperature, the
Cubbi phase appears very quickly in 10 s. After turning off the irradiation, the original SmC phase is
quickly recovered. To elucidate the mechanism at the molecular level, we monitored the transition
by grazing-incidence X-ray diffraction and Fourier transform infrared spectroscopy. An important
conclusion derived is that the trans−cis photoisomerization of the doped molecules in the mixture
do not directly cause the Cubbi phase formation, but rather gives rise to destabilization of the SmC
phase with layered structure, indirectly favoring the formation of the Cubbi phase with a twisted
molecular arrangement [4]. The details are given on the day of presentation.
References
[1] V. Luzzati and P. A. Spegt, “Polymorphism of Lipids”, Nature, vol. 215, 701–704, 1967.
[2] S. Kutsumizu, “Recent Progress in the Synthesis and Structural Clarification of Thermotropic Cubic Phases”, Isr. J.
Chem., vol. 52, 844−853, 2012.
[3] R. Hori, D. Furukawa, K. Yamamoto, and S. Kutsumizu, “Light-Driven Phase Transition in a Cubic-Phase-Forming
Binary System Composed of 4′-n-Docosyloxy-3′-nitrobiphenyl-4-carboxylic Acid and an Azobenzene Derivative”,
Chem. Eur. J. vol. 18, 7346−7350, 2012.
[4] R. Hori, Y. Miwa, K. Yamamoto, and S. Kutsumizu, “Phase Structure and Phase Transition Mechanism for LightInduced Ia3d Cubic Phase in 4′-n-Docosyloxy-3′-nitrobiphenyl-4-carboxlic acid/Ethyl 4-(4′-n-docosyloxyphenylazo)benzoate Binary Mixture”, J. Phys. Chem. B, vol. 118, 3743−3749, 2014.
Electric field tuning of optoelastic trapping in nematic liquid crystals
F. Simoni1*, L. Criante1,2, L. Lucchetti1, E. Brasselet3
1
2
Dip. SIMAU, Univ. Politecnica delle Marche, Ancona, Italy
Center for Nano Science and Technology@PoliMi, IIT, Milano, Italy
3
Univ. Bordeaux and CNRS, LOMA, Talence, France.
We report the effects of electric field on the optoelastic interaction occurring between a colloidal
particle dispersed in a nematic liquid crystal (nematic colloid) and a “ghost” colloid which results from
the local distortion of the nematic induced by a laser beam. The optoelastic interaction is induced by
minimization of the elastic free energy of the system leading to particle trapping by the ghost colloid,
as is the case occurring between two real colloidal particles. The effect has been investigated under
experimental conditions which prevents the occurrence of conventional optical trapping induced by
high gradient optical fields.
We show that application of a low frequency (1 KHz) electric field to a homeotropic sample of a
nematic liquid crystal is able to control the strength and the range of the force acting on the nematic
colloid. In case of liquid crystal with positive dielectric anisotropy the existence of a quenching
voltage is demonstrated above which no interaction takes place, while in case of negative dielectric
anisotropy an extremely large interaction range is demonstrated. Interaction range of few hundred
microns has been observed.
The experimental observations are well described by a conceptually intuitive analytical model that
accounts for the electrical realignment of the liquid crystal along the electric field direction and the
overlap between the long-range orientation distortion around both colloids.
References
1)
2)
L. Criante, F. Bracalente, L. Lucchetti, F. Simoni, E. Brasselet – Electrically tunable optoelastic
interaction range of nematic colloids – SOFT MATTER 9, 5459 (2013)
F. Simoni, S.Lalli, L. Lucchetti, L. Criante, E. Brasselet –Enhanced optoelastic interaction range in
liquid crystals with negative dielectric anisotropy - APPLIED PHYSICS LETTERS 104, 011112 (2014)
Photoalignment of liquid crystalline polymers commanded from the free surface
Takahiro Seki 1, Kei Fukuhara1, Mitsuo Hara1, Shusaku Nagano2
1. Department of Molecular Design and Engineering, Graduate School of Engineering,
Nagoya University, Chikusa, Nagoya 464-8603, Japan
2. Nagoya University Venture Business Laboratory, Chikusa, Nagoya 464-8603, Japan
e-mail: tseki@apchem.nagoya-u.ac.jp
To date, the surface alignment of liquid crystal (LC) materials has been achieved on solid surfaces
[1]. Here, we propose approaches to control the orientation of LCs from the free (air) surface side: a
photoresponsive skin layer at the free surface is prepared on a non-photoresponsive LC polymer
film by surface segregation or inkjet printing an azobenzene (Az)-containing liquid crystalline block
copolymer. In general, rodlike mesogens tend to orient vertically with the free surface (substrate)
plane. However, we found that, in films of a block copolymer comprising of PBMA (amorphous
polymer) and Az-containing LC polymer (PBMA-b-PAz), the Az mesogen is preferentially oriented
parallel to the substrate [2]. This is attributed to the segregation of the PBMA block at the topmost
(free) surface. The lower surface tension with high flexibility of the PBMA block results in the
segregation to the free surface.
When a small amount of PBMA-b-PAz is mixed with non-photoresponsive LC polymers
(for example, PPBz in Figure 1), this block copolymer segregates at the free surface by annealing.
This process leads to an orientatinal transition from a homeotropic to a planar mode. Once a preplanar orientation is obtained, the Az mesogens are readily aligned homogeneously by linearly
polarized light (LPL) irradiation. This process can be applied to birefringence photopatterning. LPL
is first irradiated in the entire film area, and
successively patterned irradiation is made with
orthogonal LPL. These procedures provide
birefringence patterning of the PPBz film.
Rotation of the crossed polarizers leads to
alternations of the bright or dark tones. This
two-step process indicates that the mesogens
can be re-aligned by another LPL. The nonphotoresponsive mesogens up to 10 Pm
thickness can be achieved by the
photoresponsive PBMA-b-PAz skin layer of ca.
20 nm thickness existing at the free surface.
Another type of patterning can be achieved by
inkjet printing of PBMA-b-PAz on the surface
of LC polymer films. Details will be discussed
in the workshop. This polymer works as
Figure 1. (a) Command surface effect from a solid surface. (b)
“command surface ink” [3].
command effect from a photoresponsive layer at the free surface.
References
[1] T. Seki, S. Nagano, and M. Hara, “Versatility of photoalignment techniques: From nematics to a wide range of
functional materials”, Polymer, vol. 54, 6053-6072 (2013)
[2] K. Fukuhara, Y. Fujii, Y. Nagashima, M. Hara, S. Nagano, and T. Seki, “Liquid crystalline polymer and block
copolymer domain alignment controlled by free-surface segregation”, Angew. Chem. Int. Ed. Vol. 52, 5988-5991, 2013.
[3] K. Fukuhara, S. Nagano, M. Hara, and T. Seki, “Free-surface molecular command systems for photoalignment of
liquid crystalline materials”, Nat. Commun., vol. 5 p. 3320, 2014.
Lasing in Liquid Crystals driven to Chaos: Plasmon-Exciton Coupling
Enhances Scattering and Gain
J. Osborne1, A. De Luca2, M. Infusino1,2, F. Carbone3, C. Versace2 and G. Strangi1,2*
1 Department of Physics, Case Western Reserve University, Cleveland OH (USA).
2 LICRYL CNR-IPCF, Department of Physics, University of Calabria, Rende (Italy)
3 School of Mathematical Sciences, University College Dublin, Dublin (Ireland)
The scientific interest for disordered multiply scattering systems find its basis on the gigantic
resonance effects experienced by light-waves travelling along random trajectories in complex
and rapidly changing structures. These effects originate by localization processes that take place
when the Motte-Ioffe-Regel criterion is satisfied. In recent years, optical localization
phenomena have been invoked as responsible of feedback mechanisms in laser action[1-2].
In this work, we report chaotic laser action in complex fluids (liquid crystals doped with gain
functionalized plasmonic nanostructures), driven towards states of increasing stochasticity
generated by electro-convective turbulence. We will discuss how the fractal fragmentation of
dynamic domains in different turbulent
regimes leads to excitation of
low-threshold lasing modes that exhibit
spectral and temporal characteristics of a
chaotic laser oscillator. Another striking
aspect of this work is related to the the
gain-plasmon interplay in nanoparticle
dispersed liquid crystalline materials,
where a resonant energy transfer process
occur during optical excitation [3-5].
These results shed some new light about
the plasmonic control of the modes
selection mechanism, since only some of
the modes coupled to the plasmon states
survive the lasing modes competition effect. Hence, plasmonic resonances and light localization
processes owing to intense recurrent dynamical scattering are behind a reconfigurable dynamic
laser, characterized by external control of turbulent processes occurring in dynamic scattering
regimes.
References:
[1] G. Strangi, S. Ferjani , V. Barna Optics Express 14,17 7737-7744 (2006)
[2] S.Ferjani,L. Sorriso-Valvo, A. De Luca, G. Strangi, Physical Review E 78, 1 011707 (2008).
[3] G. Strangi, A. De Luca, S. Ravaine, M. Ferr and R. Bartolino, Appl. Phys. Lett., 98, 251912 (2011),
[4] A. De Luca, M. P. Grzelczak, I. Pastoriza-Santos, L. M. Liz-Marzán, M. L. Deda, M. Striccoli and G.
Strangi, ACS Nano, 5, 5823–5829 (2011)
[5] A. De Luca, M. Ferrie, S. Ravaine, M. La Deda, M. Infusino, A.R. Rashed, A. Veltri, A. Aradian, N.
Scaramuzza and G. Strangi, J. Mater. Chem., 22, 8846 (2012)
_____________________________________________
* Giuseppe Strangi; E-mail: Gxs284@case.edu Photomobile Polymer Materials: Structures and Functions
Tomiki Ikeda, Kiyohide Takado, Toru Ube
Research & Development Initiative, Chuo University, Tokyo 112-851, Japan
e-mail:tikeda@tamacc.chuo-u.ac.jp
Crosslinked liquid-crystalline polymers (CLCPs) are a class of materials that show macroscopic
deformation in response to actinic light [1]. These materials contain aligned mesogenic units as well
as photochromic moieties with a crosslinked structure, and deform reversibly upon exposure to
actinic light, resulting from reversible photochromic reactions of the photoresponsive group. This
photochemical reaction results in photoinduced phase transition or reduction in order parameters of
mesogens [2], leading to a subsequent anisotropic deformation thanks to a strong coupling between
the molecular order and the crosslinked polymer structures [3,4]. CLCPs as photomobile polymer
materials have been intensively investigated due to their large photomechanical effects, which have
enabled the fabrication of unique devices such as rotors [5], cilia [6], lenses [7], inch worm [8] and
robotic arms [9].
Crosslinking in CLCPs is usually formed by covalent bonds, which produces insoluble samples.
Crosslinking with non-covalent bonds may lead to a better processing of CLCPs. We used lowmolecular-weight crosslinkers with hydrogen-bond acceptors to form crosslinking among polymers
bearing hydrogen-bond donors by hydrogen bonding [10]. The film showed bending upon exposure
to UV light and the bent film reverted to the initial state by irradiation with visible light just as the
covalently crosslinked LCPs. The LCP film crosslinked by hydrogen bonding was soluble in THF,
enabling recovery, reuse and recycle of the starting materials. However, they are not mechanically
stable enough for various applications. We prepared
azobenzene LC polymer fibers, crosslinked by
hydrogen bonding, containing chemically modified
single-walled carbon nanotubes (SWNTs) as a filler
(Figure 1), which exhibit reversible bending upon
exposure to actinic light. The tensile stress and
mechanical force generated by irradiation with UV light
much increased by incorporation of a small amount of
SWNTs, which is quite advantageous in various
applications of these materials [11].
Figure 1. CLCP with chemically modified SWNTs
References
[1] a) T. Ikeda, J. Mamiya, Y. Yu, Angew. Chem. Int. Ed., 46, 506, 2007. b) H. Yang, G. Ye, X.Wang, P. Keller, Soft
Matter, 7, 815, 2011. c) C. Ohm, M. Brehmer, R. Zentel, Adv. Mater., 22, 3366, 2010. d) T. Ube, T. Ikeda, Angew.
Chem. Int. Ed., in press.
[2] a) S. Tazuke, S. Kurihara, T. Ikeda, Chem. Lett., 991, 1987. b) T. Ikeda, O. Tsutsumi, Science, 268, 1873, 1995.
[3] P. G. de Gennes, C. R. Acad. Sci. B, 281, 101, 1975.
[4] a) H. Finkelmann, E. Nishikawa, G. G. Pereira, M. Warner, Phys. Rev. Lett., 87, 015501, 2001. b) Y. Yu, M.
Nakano, T. Ikeda, Nature, 425, 145, 2003.
[5] M. Yamada, M. Kondo, J. Mamiya, Y. Yu, M. Kinoshita, C. J. Barrett, T. Ikeda, Angew. Chem. Int. Ed., 47, 4986,
2008.
[6] C. L. van Oosten, C. W. M. Bastiaansen, D. J. Broer, Nat. Mater., 8, 677, 2009.
[7] S. Xu, H. Ren, Y. Lin, M. G. J. Moharam, S. Wu, N. Tabiryan, Opt. Express, 17, 17590, 2009.
[8] M. Yamada, M. Kondo, R. Miyasato, Y. Naka, J. Mamiya, M. Kinoshita, A. Shishido, Y. Yu, C. J. Barrett, T. Ikeda,
J. Mater. Chem., 19, 60, 2009.
[9] F. Cheng, R. Yin, Y. Zhang, C. Yen, Y. Yu, Soft Matter, 6, 3447, 2010.
[10] J. Mamiya, A. Yoshitake, M. Kondo, Y. Yu, T. Ikeda, J. Mater. Chem., 18, 63, 2008.
[11] T. Ozawa, M. Kondo, J. Mamiya, T. Ikeda, J. Mater. Chem. C, 2, 2313, 2014.
Orientational order parameters for low-symmetry liquid crystals
Stefano Turzi 1
1. Dipartimento di Matematica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano, Italy.
Nematic liquid crystals are usually assumed to have uniaxial symmetry. However, many real
mesogens do not possess such symmetry. It is therefore natural, and possibly important for
applications, to extend the theories of liquid crystals to lower molecular and phase symmetries.
Since 1970, when Marvin Freiser of IBM predicted that molecules possessing D 2h symmetry could
form a biaxial nematic phase [1], chemists have been attempting to synthesize such a liquid crystal.
While lyotropic biaxial phases were found, a thermotropic phase proved more difficult to create.
In 2004 there has been the experimental claim that bent-core molecules may form the elusive
biaxial nematic phase. Since then, interest in biaxial phases has increased significantly.
However, the extensions of the existing theories to lower symmetries are far from trivial as we try
to show during the presentation. In particular, we only explore some recent developments in the
theory of low-symmetry nematics [2]. Namely, we discuss the abstract definition of orientational
order parameters in a general setting. These are the bulding blocks for the construction of
molecular-field and Landau theories to describe the phase behaviour of biaxial nematics (D 2h) and
C2h-nematics.
Figure 1. A sketch of the idealized molecule with D2h point group symmetry. The unit vectors lx , ly , and lz represent the
laboratory axes; mx , my , and mz represent the molecular axes. The Euler angles α, β, and γ are also shown.
[1] M. J. Freiser, “Ordered states of a nematic liquid”, Phys. Rev. Lett., vol. 24, p. 1041-1043, 1970.
[2] S. S. Turzi, “On the Cartesian definition of orientational order parameters”, J. Math. Phys., vol. 52, p. 053517, 2011.
SICL-JLCS WORKSHOP
and
SICL MEETING
POSTERS
Macroscopic Order in a Nematic Liquid Crystal: Perturbation by
Spontaneous Director Fluctuations
Rauzah Hashim 1, Atsuhiro Kasatani 2, Geoffrey R. Luckhurst 3,
Akihiko Sugimura 2, Bakir A. Timimi 3, Herbert Zimmermann 4
1. School of Chemistry, University of Malaya, Kuala Lumpur, Malaysia
2. School of Information Systems Engineering, Osaka Sangyo University, 3-1-1 Nakagaito, Daito-Shi, Osaka
574-4853, Japan
3. School of Chemistry, University of Southampton, Highfield, Southampton, SO17 1BJ, United Kingdom
4. Department of Biophysics, Max-Planck-Institut für Medizinische Forschung, Jahnstrasse 29, D-69120
Heidelberg, Germany
e-mail: sugimura@ise.osaka-sandai.ac.jp
The anisotropic nature of liquid crystalline materials is commonly defined by the presence of a
single director. This can be manipulated by external factors including homogeneous electric and
magnetic as well as inhomogeneous surface fields. It is therefore of prime importance to understand
the alignment of the nematic director by either a magnetic and/or an electric field by careful
evaluation of the hydrodynamic processes under both equilibrium and non-equilibrium conditions
[1]. Deuterium nuclear magnetic resonance (DNMR) spectroscopy has been used to investigate the
static [2,3] and dynamic [4] phenomena. Here the director is aligned by the magnetic field of the
spectrometer and the application of an electric field produces a non-equilibrium state resulting in
rotation of the director. This powerful technique has proved to be especially important for the
investigation of director alignment in liquid crystals.
We report on the study of the anomalous director distribution, observed and predicted, during
the director reorientation in a nematic liquid crystal film subject to near orthogonal magnetic and
electric fields. Time-resolved DNMR spectroscopy has been employed to investigate the
homogeneous field-induced director dynamics. This technique has the advantage of being able to
explore the director distribution during the electric field-induced rotation of the director. Our timeresolved NMR experiments have revealed a surprising result that the alignment of the director can
pass through a series of non-uniform states. This is especially true when the angle between the two
fields approaches 90°. The macroscopic order has been perturbed, although the initial and final
states of the director appear to be essentially uniform. However, the initial state does have a
profound influence on the uniformity of the director in the intermediate states.
The spectra observed in such experiments can be accounted for with the simple assumption that
at the end of the magnetic preparation time the director is not uniformly aligned. As a consequence
when the two fields are almost orthogonal the different regions associated with the initial director
distribution move at significantly different rates thus enhancing the non-uniformity in the director
distribution. Those regions are initiated by the thermal director fluctuation.
References
[1] A. Sugimura and G. R. Luckhurst, “Liquid-crystalline samples: static and dynamic measurements of director
alignment”, Encyclopedia of Magnetic Resonance, vol.2, emrstm1321, pp.307-314 (Wiley, 2013).
[2] D. Hamasuna, G. R. Luckhurst, A. Sugimura, B. A. Timimi and H. Zimmermann, “Director Alignment by Crossed
Electric and Magnetic Fields: A Deuterium NMR Study”, Phys. Rev. E, vol.84, pp.011705-1-11, 2011.
[3] A.Veron, et al., “Properties of the static NMR response of a confined thin nematic film of 5CB-d2 under crossed
electric and magnetic fields: Theory and experiments”, Phys. Rev. E, vol.86, pp.051708-1-20, 2012.
[4] G. R. Luckhurst, T. Miyamoto, A. Sugimura, B. A. Timimi, “Director reorientation processes in a monodomain thin
nematic liquid crystal film: A deuterium NMR spectroscopy study”, J. Chem. Phys., vol.117, pp.5899-5907, 2002.
Acknowledgements: This work was supported by a Grant-in Aid for Scientific Research (B-24360127) of the Japan
Society for the Promotion of Science (JSPS).
ESR characterization of BaTiO3 ferroelectric nanoparticles
suspended in a nematic liquid crystal
Isabella Miglioli, Alberto Arcioni, Claudio Zannoni
Dipartimento di Chimica Industriale “Toso Montanari” and INSTM, Università, Viale Risorgimento 4, I40136 Bologna, Italy
isabella.miglioli2@unibo.it
The effects of suspending ferroelectric nanoparticles in a highly ordered, commercial nematic
liquid crystal (LC) have been studied using the EPR spin probe technique.
Dilute suspensions of ferroelectric nanosized particles in a nematic liquid crystal (LC) have
been reported to display interesting properties that can be used to improve the LC technology
[1-4]. On the one hand, the presence of a well dispersed, small amount (0.1 – 1 %) of these
nanoparticles does not induce any considerable LC director deformation so that the LC
colloid behaves optically as a pure LC [1]. On the other, the dispersion can modify the
nematic-isotropic transition temperature, increase the degree of nematic order, enhance, due
to the permanent spontaneous polarization of the particle's material, the local dielectric
anisotropy, and the sensitivity to an applied electric field, consequently improving the rate of
the field-induced director reorientation. Practically, these dispersions are a way to combine
the advantages of nematics (such as the ease of alignment) and the electro-optical response,
typical of ferroelectric LCs [2,3,5,6].
Here, the ESR spin probe technique, which has already been successfully applied to
characterize other complex liquid crystalline systems [7,8], was employed to determine
nematic-isotropic transition temperatures, modifications in the nematic director configuration
and local molecular order and dynamics of a 0.5% and a 1% dispersion of BaTiO3
ferroelectric nanoparticles in the BL038 nematic LC. Differently from what is reported in
literature, at increasing nanoparticle concentration the transition shifts to lower temperatures
by a few kelvin, and the nematic order shows a small decrease accompanied by no substantial
alteration of the reorientational dynamics.
References:
[1] Y. Reznikov, O. Buchnev, O. Tereshchenko, V. Reshetnyak, A. Glushchenko, and J. West., “Ferroelectric
nematic suspension”, Appl. Phys. Lett., v. 82, p. 1917, 2003.
[2] O. Kurochkin, H. Atkuri, O. Buchnev, A. Glushchenko, O. Grabar, R. Karapinar, V. Reshetnyak, J. West, and
Yu. Reznikov, “Nano-colloids of Sn2P2S6 in nematic liquid crystal pentyl-cyanobyphenile”, Condensed Matter
Physics, v.13, p.33701, 2010.
[3] N. Podoliak, O. Buchnev, O. Buluy, G. D' Alessandro, M. Kaczmarek, Y. Reznikov, and T. J. Sluckin,
“Macroscopic optical effects in low concentration ferronematics” Soft Matter, v. 7, p. 4742, 2011.
[4] S. A. Basun, G. Cook, V. Yu. Reshetnyak, A. V. Glushchenko, and D. R. Evans, “Dipole moment and
spontaneous polarization of ferroelectric nanoparticles in a nonpolar fluid suspension”, J. Phys. Chem. B, v. 84,
p. 024105, 2011.
[5] A. Mertelj, L. Cmok, M. Copic, G. Cook, and D. R. Evans, “Critical behavior of director fluctuations in
suspensions of ferroelectric nanoparticles in liquid crystals at the nematic to smectic-a phase transition”, Phys.
Rev. E, v. 85, p. 021705, 2012.
[6] F. Li, O. Buchnev, C-I. Cheon, A Glushchenko, V. Reshetnyak, Yu. Reznikov, T. J. Sluckin, and J. L. West,
“Orientational coupling amplification in ferroelectric nematic colloids”, Phys. Rev. Lett., v. 97, p. 147801, 2006.
[7] A. Arcioni, C. Bacchiocchi, I. Vecchi, I. Venditti, and C. Zannoni, “ A comparison of the e
ffects of dispersed hydrophobic or hydrophilic aerosil nanoparticles on the order and dynamics of the 5CB liquid
crystal”, Chem. Phys. Lett., v. 396, p.433, 2004.
[8] C. Bacchiocchi, I. Miglioli, A. Arcioni, I. Vecchi, K. Rai, A. Fontecchio, C. Zannoni, “Order and dynamics
inside H-PDLC nanodroplets: an ESR spin probe study”, J. Phys. Chem. B, v. 113, p. 5391, 2009.
Aknowledgement: We thank D. R. Evans, G. Cook for providing BaTiO3 harvested nanoparticles and the
European Office of Aerospace Research & Development (EOARD) for financial support.
Molecular Organization of Nematic Liquid Crystals Between
Concentric Cylinders: Role of the Elastic Anisotropy
C. Chiccoli 1, P. Pasini 1, L.R. Evangelista 2, R.T. Teixeira-Souza 3, C. Zannoni 4
1
Istituto Nazionale di Fisica Nucleare, Sezione di Bologna, Via Irnerio 46, I-40126 Bologna, Italy
2
Departamento de Fisica, Universidade Estadual de Maringà
Avenida Colombo, 5790-87020-900 Maringà, Paranà, Brazil
3
4
Universidade Tecnològica Federal do Paranà, Campus Apucarana,
Rua Marcìlio Dias 635, 86812-460 Apucarana, Paranà, Brazil
Dipartimento di Chimica Industriale “Toso Montanari” and INSTM, Università,
Viale Risorgimento 4, I-40136 Bologna, Italy
Lattice simulations where a small cluster of neighbouring molecules is represented simply by
a head-less vector (“spin”) have been employed in investigating orientational properties of
liquid crystals (LC) since the pioneering work of Lebwohl and Lasher [1]. Simple lattice
models are particularly useful for the investigation of confined systems [2] and complex
geometries, where the analytical treatment with the elastic theory may be prohibitive and
sometimes has to be restricted to a few approximate situations [3]. In these cases, potentially
relevant from the applicative point of view, lattice simulations employing suitable chosen
potentials are helpful and can be implemented in a very efficient way [4]. Likewise, the study
of defects is particularly suitable to being attacked by computer simulations [5].
The aim of the present paper is to use Monte Carlo simulations to investigate the role of the
elastic anisotropy on the spontaneous deformations of nematic liquid crystals trapped between
concentric cylinders [6-9]. Strong anchoring and homeotropic orientation, parallel to the
radial direction, are implemented at the confining surfaces. The elastic anisotropy is taken
into account in the bulk interactions by using the pair potential introduced by Grunh and Hess
[10] and parametrized by Romano and Luckhurst, the so-called GHRL potential [11]. In the
case of equal elastic constants, a small, but appreciable, deformation in the Z direction is
observed, while when the values of K11/K33 if K22=K33 are low enough all the spins in the
bulk follow the orientation imposed by the surfaces. For larger values of K11/K33
spontaneous deformations, perpendicular to the polar plane, increase significantly. Our
findings indicate that the onset of these deformations also depends on the ratio K22/K33 and
on the radius of the cylindrical surfaces. Although expected from the elastic theory, no
tangential component of the deformations was observed in the simulations for the set of
parameters analyzed.
References:
[1] P. A. Lebwohl and G. Lasher, Phys. Rev. A 6, 426 (1972).
[2] P Pasini, C. Chiccoli, and C. Zannoni in Advances in the Simulations of Liquid Crystals, (Kluwer
Academic, Dordrecht, 2000), edited by P. Pasini and C. Zannoni.
[3] G. Barbero and L. R. Evangelista, An Elementary Course on the Continuum Theory for Nematic Liquid
Crystals, (World Scientific, Singapore, 2001).
[4] C. Chiccoli, P. Pasini, F. Semeria, C. Zannoni, Mol. Cryst. Liq. Cryst. 212, 197 (1992).
[5] See e.g., O. D. Lavrentovich, P. Pasini, C. Zannoni and S. Zumer (eds), Defects in Liquid Crystals:
Computer Simulations, Theory and Experiment (Kluwer Academic, Dordrecht, 2001).
[6] H. Tsuru, J. Phys. Soc. Jpn. 59, 1600 (1990).
[7] D. R. M. Williams and A. Halperin, Phys. Rev. E 48, R2366, (1993).
[8] G. Bevilacqua and G. Napoli, Phys. Rev. E 81, 031707 (2010).
[9] R. Teixeira de Souza et al, Physica A, 389, 945-950 (2010).
[10] T. Gruhn and S. Hess, Z. Naturforsch A 51, 1 (1996).
[11] G.R. Luckhurst and S. Romano, Liq. Cryst. 26, 871 (1999).
Molecular dynamics simulations of 8CB smectic thin films
Mattia Felice Palermo, Luca Muccioli, Claudio Zannoni
Dipartimento di Chimica Industriale “Toso Montanari”, Università di Bologna, Viale Risorgimento 4, I-40136,
Bologna, Italia
mattiafelice.palerm2@unibo.it
Atomistic computer simulations have been recently shown to be able to predict realistic values for
observables such as transition temperatures, orientational order parameters, etc, particularly for
cyanobiphenyls [1]. In a recent work [2] we have extended this investigation to the study of bulk
smectics like 4-n-octyl-4′cyanobiphenyl (8CB), showing that layer spacing and positional order
parameters can be obtained. Here we wish to show the first application to free standing smectic thin
films that have been recently studied in literature [3]. These systems have a high degree of
uniformity: the alignment of smectic layers is almost perfect, allowing to build single-domain
samples of various thicknesses. This makes them an ideal model for studying low-dimensional
fluctuation behaviour and phase transitions. We report the results of atomistic molecular dynamics
(MD) simulations of 8CB thin films of 1'500 and 12'000 molecules, with a number of smectic layers
ranging from 1 to 10. The MD technique also allowed us to build and characterize films with a non
integer number of layers, which are experimentally known to be unstable. The influence of the two
vacuum interfaces and the extent of its propagation along the films have been studied in terms of
orientational, positional order parameters and layer spacing, and results were compared with
theoretical models. We have also characterized the trend of surface tension as a function of the
number of layers and determined possible changes in the phase transition sequence with respect to
the one of bulk systems.
References
[1] G. Tiberio, L. Muccioli, R. Berardi and C. Zannoni, “Towards in silico liquid crystals. Predicting molecular
organization and phase transitions for n-cyanobiphenyls via molecular dynamics simulations”, ChemPhysChem, 2009,
10, 125-136
[2] M. F. Palermo, A. Pizzirusso, L. Muccioli and C. Zannoni, “An atomistic description of the nematic and smectic
phases of 4-n-octyl-4'cyanobiphenyl (8CB)”,J. Chem. Phys., 2013, 138, 204901-204916
[3] C. Bohley and R. Stannarius, “Inclusions in free standing smectic liquid crystal films”,Soft Matter, 2008, 4, 683-702
Acknowledgment: We thank Emilia-Romagna region for a Spinner postgraduate fellowship granted to M.F.P., MIUR
PRIN national project “Novel ordered systems for high response molecular devices” for funding this research, and
CINECA Supercomputing Center for providing computer time through the ISCRA scheme.
Thermodynamic and chemical-physical characterization of a binary
mixture made of photosensitive and liquid crystalline molecules
Eleonora Borrello1, Mario Cifelli1, Valentina Domenici1*, Celia Duce1, Maria Rosaria Tine'1,
Vera Hamplova2 and Gabriela Ambrozic3
1. Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via Risorgimento 35, 56126 Pisa, Italy.
2. Department of Dielectrics, Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 182 21
Prague, Czech Republic.
3. National Institute of Chemistry, Hajdrihova ulica 19, 1001, Ljubljana, Slovenia.
e-mail: valentina.domenici@unipi.it
In this study, we have prepared binary mixures of two rod-like molecule: a photosensitive
azobenzene derivative (called J7) and a mesogen forming nematic and smectic A phases (called
M11). The interest in these two compounds is related to their use to prepare photo-active liquid
crystalline elastomers (LCEs), for optical applications.[1-3] In these LCEs, the relative
concentration of these two molecules, used as co-monomers, is crucial to have the desired thermomechanical and optical properties.
Our goal was to build the phase diagram of the binary system J7-M1. Differential calorimetry
(DSC) and polarized optical microscopy (POM) were used to characterize the mesophase behavior,
and the stability of the mesophases of several J7-M1mixtures at different molar ratios.
Moreover, 2H NMR spectroscopy of the selectively labelled M11, as it is and in different mixtures
of J7-M11, was applied to study the orientational order (Szz) and its trend with the temperature.
References
[1] Marko Gregorc, Boštjan Zalar, Valentina Domenici, Gabriela Ambrožič, Irena Drevenšek-Olenik, Martin Fally,
Martin Čopič, “Depth Profile of Optically Recorded Patterns in Light-Sensitive Liquid Crystal Elastomers”, Phys. Rev.
E, vol. 84, pp. 031707, 2011.
[2] Marko Gregorc, Hui Li, Valentina Domenici, Gabriela Ambrožič, Martin Čopič, Irena Drevenšek-Olenik, “Optical
properties of light-sensitive liquid-crystal elastomers in the vicinity of the nematic-paranematic phase transition”, Phys.
Rev. E, vol. 87, p. 022507. 2013.
[3] Marko Gregorc, Hui Li, Valentina Domenici, Irena Drevenšek-Olenik, “Tunable photonic structures from liquid
crystal elastomers”, Proc. SPIE 8556, Holography, Diffractive Optics, and Applications V, 855616 (November 26,
2012); doi:10.1117/12.2000624.
Acknowledgment: Effort sponsored by the French-Italian University “Galilei cooperation project 2012-2013”. This
work was also supported by Czech projects ASCR M100101204 and ASCR M100101211. PRIN 2010-2011 n.
2010C4R8M8 entitled “NANOSCALE FUNCTIONAL ORGANIZATION OF (BIO)MOLECULES AND HYBRIDS FOR
TARGETED APPLICATION IN SENSING, MEDICINE AND BIOTECHNOLOGY” is also acknowledged for financial
support.
Conformational Properties and Orientational Order of a de Vries
Liquid Crystal by NMR Spectroscopy
Valentina Domenici1*, Moreno Lelli2, Mario Cifelli1, Vera Hamplova3,
Alessandro Marchetti2 and Carlo Alberto Veracini1
1. Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via Risorgimento 35, 56126 Pisa, Italy.
2. CNRS/ENS Lyon, Centre de RMN à Très Hauts Champs, 5 rue de la Doua, 69100 Villeurbanne, France.
3. Department of Dielectrics, Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 182 21
Prague, Czech Republic.
e-mail: valentina.domenici@unipi.it
Solid-state and liquid-state NMR spectroscopic techniques are used to describe at molecular level
the behaviour of a de Vries liquid crystal (9HL) at the SmA–SmC* transition, which is
characterized by the absence of the layer shrinkage, typical of non-de Vries smectogens. Previous
2
H NMR studies [1] on the same smectogen, performed at a different magnetic field provided
evidence of the occurrence of a tilt of one of the three phenyl rings, constituting the aromatic core
of 9HL, at the SmA–SmC* phase transition. In this work, the study is extended to the whole rigid
aromatic core of the 9HL. In particular, the variable temperature behavior of the mesogen studied
by 1D 13C NMR cross-polarization (CP) and 2D 1H–13C PDLF (proton-encoded 13C-detected, local
field) NMR experiments made possible the characterization of the conformational and orientational
properties in the two smectic phases [2].
Figure 1. Simple sketch of the conformational change of the de Vries mesogen 9HL at the SmA-SmC* transition according to
NMR investigations. [2]
References
[1] A. Marchetti, V. Domenici, M. Cifelli, C.A. Veracini, V. Novotna, A. Lesage, M. Lelli, “Direct Measure of the Tilt
Angle in de Vries-Type Liquid Crystals through NMR Spectroscopy”, ChemPhysChem, vol. 11, p. 1641-1645, 2010.
[2] V. Domenici, M. Lelli, M. Cifelli, V. Hamplova, A. Marchetti, C. A. Veracini, “Conformational Properties and
Orientational Order of a de Vries Liquid Crystal by NMR Spectroscopy”, ChemPhysChem 2014, in press, DOI:
10.1002/cphc.201301036.
Acknowledgment: Effort sponsored by the French-Italian University “Galilei cooperation project 2012-2013”. This
work was also supported by Czech projects ASCR M100101204 and ASCR M100101211.
Spin-spin ILT colloidal morphology analysis and mechanical
properties of ultrasound cumb rubber modified bitumen
Cesare Oliviero Rossi1, Luigi Filippelli1, Luigi Gentile1, Noemi Baldino2
1 Department of Chemistry and Chemical Technology, University of Calabria, Via P. Bucci, Cubo 14/D - 87036
Arcavacata di Rende - Cosenza – ITALY
2 Department of Department of Informatics, Modeling, Electronics and Systems Engineering (D.I.M.E.S.), University of
Calabria, Via P. Bucci, - 87036 Arcavacata di Rende - Cosenza - ITALY
e-mail: cesare.oliviero@unical.it
s
Approximately 9 to 10 kg of rubber from tyres per inhabitant and year are currently discarded in the
industrialized societies. In adddition rutting and fatigue cracking are the major distresses for road
pavement performances [1-2]. Therefore, the addition of crumb rubber (CR) in the production of
asphalt rubber (AR) mixes for road pavements should be considered as a sustainable technology to
transform an unwanted residue into a new bituminous mixture highly resistant to fatigue and
fracture [3]. In this process, the wasted rubber needs to be devulcanized (UCRM). In the present
work base bitumens interacted with neat crumb and ultrasound devulcanized crumb rubber to
produce AR mixes. Nuclear magnetic resonance and Rheology dynamic experiments were
functional to investigate the influence of ultrasound treated crumb rubber modifier on the morphostructure and rheological properties of bitumen binder. The partial devulcanization of the CR by
ultrasounds, resulted into enhanced mechanical properties in a wide range of temperatures.
Figure 1. Time cure tests for neat bitumen (NB), not devulcanized bitumen (NVRB), partially devulcanized rubberized
bitumens.
References
[1] N. Baldino, D. Gabriele, C. Oliviero Rossi, L. Seta, F. R. Lupi, P. Caputo, " Low temperature rheology of
polyphosphoric acid (PPA) added bitume", Constr. Build. Mater.,36, 592-598, 2012.
[2] L. Filippelli, L. Gentile, C. Oliviero Rossi, G. A. Ranieri, F. Antunes, " Structural Change of Bitumen in the
Recycling Process by Using Rheology and NMR", Ind. Eng. Chem. Res., 51, 16346-16353, 2013.
[3] M. Heitnaaan “Design and Construction of Asphalt Paving Malerials with Crumb Rubber Modifier”, Transp. Res.
Rec., 1, 8, 1339 – 1345, 1992
SICL MEETING
TALKS
Liquid crystal tuneable plasmonic devices
Dimitrios C. Zografopoulos and Romeo Beccherelli
Consiglio Nazionale delle Ricerche, Istituto per la Microelettronica e Microsistemi, 00133, Roma, Italy
e-mail: romeo.beccherelli@artov.imm.cnr.it
We will review our recent work on guided optics plasmonic devices tuneable by means of liquid
crystals. Optical attenuators and switches in the Long Range Surface Plasmon Polariton (LRSPP)
configurations will be discussed. Then, LRSPP directional couplers in both coplanar and vertical
configuration will be presented. The combination of these couplers allows to design multilevel
couplers for complex plasmonic circuits and routing.
Figure 1. Schematic illustration of coplanar and vertical directional couplers.
References
[1] D. C. Zografopoulos and R. Beccherelli “Plasmonic Variable Optical Attenuator Based on Liquid-Crystal Tunable
Stripe Waveguides”, Plasmonics, vol. 8, pp. 599-604, 2013
[2] D. C. Zografopoulos, R. Beccherelli, A. C. Tasolamprou and E. E. Kriezis, “Liquid-Crystal Tunable Waveguides
for Integrated Plasmonic Components” Photonics and Nanostructures – Fundamentals and Applications Vol. 11, pp. 7384, 2013
[3] D. C. Zografopoulos and R. Beccherelli “Long-range plasmonic directional coupler switches controlled by
nematic liquid crystals” Optics Express, Vol. 21 pp. 8420-8250, 2013
[4] D. C. Zografopoulos and R. Beccherelli “Design of a vertically-coupled liquid-crystal long-range plasmonic
optical switch” Appl. Phys. Lett. Vol. 102, art 101103, 2013
[5] D. C. Zografopoulos and R. Beccherelli “Liquid-crystal tunable metal-insulator-metal plasmonic waveguides and
Bragg resonators”, Journal of Optics, Vol. 15 art. 055009, 2013
Acknowledgment: Italian Ministry of Foreign Affairs, Directorate General for the Country Promotion.
Lightwave circuits based on organic materials for optical signal
filtering and switching in WDM communication systems
Giovanni Gilardi,1 Rita Asquini,2 Romeo Beccherelli3 and Antonio d’Alessandro2,3
1. University of Technology Eindhoven, Department of Electrical Engineering, Photonic Integration Group,
Eindhoven, The Netherland
2. Sapienza University of Rome, Department of Information Engineering, Electronics and Telecommunications, Via
Eudossiana 18, Rome 00184, Italy
3. CNR—Istituto per la Microelettronica e Microsistemi, 00133 Rome, Italy
Periodic structures are suitable to make wavelength selective photonic devices for a large
variety of applications ranging from fiber optic communications, biosensors, and lasers. We present
our experimental and simulation results on guided wave devices, which can be switched and tuned
electrically and optically by light driving signals in micro-and nanostructured device geometries.
Wavelength selectivity is obtained by using either the phenomenon known as whispering gallery
modes in microsphere resonator or Bragg diffraction. In both cases we consider organic materials as
medium to tune spectral response of the proposed devices.
Figure 1. (Left) Schematic view of the tunable filter based on microsphere resonator integrating liquid crystals. (Right) Schematic
view of the device with a zoom on the grating structure. In both figures the inset shows the orientation tilt (θ) and twist (φ) angles of
the molecular director.
Figure 1 (Left) shows a tunable electro-optic filter that combines the high Q-factor WGMs of the
spherical resonators and the large electro-optic effect of the LCs into a simple filter [1]. The value
of the FSR and the quality factor remains unchanged for the various values of the applied voltage.
An increase of the applied voltage increases the power coupled with the sphere and increases the
on–off ratio of the filter’s insertion loss. Figure 1 (Right) shows a polarization independent alloptical Bragg filter integrated on glass made of ion-exchanged channel waveguides and composite
holographic gratings. The filter exhibits a power suppression of more than 20 dB at the Bragg’s
wavelength. A tuning range of 6.6 nm is observed by applying an optical pump with a density
power of about 1.43W⁄cm2 [2].
[1] G. Gilardi, D. Donisi, A. Serpenguezel and R. Beccherelli, “Liquid crystal tunable filter based on microsphere
resonators”, Opt. Lett., Vol. 34, Issue 21, pp. 3253-3255 (2009).
[2] G. Gilardi, L. de Sio, R. Beccherelli, R. Asquini, A. d’Alessandro and C. Umeton, “Observation of tunable optical
filtering in photosensitive composite structures containing liquid crystals”, Opt. Lett., Vol. 36, No. 24, pp. 4755-4757
(2011).
NMR in different partially ordered media: a route for
structure, order and conformation of small flexible organic compounds
M. E. Di Pietro 1,2, G. De Luca 1, G. Celebre 1, D. Merlet 2, C. Aroulanda 2
1. Dipartimento di Chimica e Tecnologie Chimiche, Università della Calabria, via P. Bucci, 87036 Rende (CS), Italy
2. Equipe LRMN, ICMMO, Université Paris-Sud, 15 rue Georges Clemenceau, 91405 Orsay, France
e-mail: mariaenrica.dipietro@unical.it
Over the years NMR spectroscopy in partially ordered media has proved to be a flexible and
meaningful tool for dealing with orientational, positional, structural and conformational problems of
a variety of small rigid and flexible organic molecules in solution [1]. The methodology is applied
here to investigate different flexible bioactive or biomimetic molecules dissolved in both highly and
weakly ordering phases. For the first time the strategy is used to probe the conformational
distribution of some single- and two-rotor nonsteroidal anti-inflammatory drugs, belonging to the
families of salicylates and profens, dissolved in weakly orienting chiral nematic PBLG phases [2].
Starting from homo- and heteronuclear dipolar couplings, difficult to extract in thermotropic
solvents for systems of more than 10 spins, the torsional distributions of such molecules can be
satisfactory described by the Additive Potential model combined with the Direct Probability
Description of the torsional distribution in terms of Gaussian functions (AP-DPD approach [3]).
Moreover, the conformational and orientational study of two stilbenoids displaying cooperative
torsions is presented in both a highly and weakly ordering liquid crystalline solvent [4]. This
comparative study allows to draw some conclusions on reliability, accuracy and accessibility of
desired data in the two phases.
Figure 1. Torsional probability distributions obtained from experimental NMR anisotropic dipolar couplings via the AP-DPD
approach for (a) diflunisal in PBLG/THF, (b) naproxen in PBLG/THF-d8 and (c) trans-stilbene in ZLI1132.
References
[1] “NMR of Ordered Liquids”, E. E. Burnell and C. A. de Lange eds., Kluwer Academic, Dordrecht, 2003
[2] a) M. E. Di Pietro, C. Aroulanda, D. Merlet, J. Magn. Reson., vol. 234, 101-105, 2013; b) M. E. Di Pietro, C.
Aroulanda, D. Merlet, G. Celebre, G. De Luca, 2014, submitted
[3] a) J. W. Emsley, G. R. Luckhurst, C. P. Stockley, Proc. R. Soc. London, Ser. A, vol. 381, 117-138, 1982; b) G.
Celebre, G. De Luca, J. W. Emsley, E. K. Foord, M. Longeri, F. Lucchesini, G. Pileio, J. Chem. Phys., vol. 118, 64176426, 2003.
[4] a) G. Celebre, G. De Luca, M. E. Di Pietro, J. Phys. Chem. B, vol. 116, 2876-2885, 2012; G. Celebre, G. De Luca,
M. E. Di Pietro, J. Mol. Struct., vol. 1034, 283-288, 2013.
Acknowledgment: Effort sponsored by the European Commission, the European Social Fund and the Regione Calabria
through the cofunded Ph.D. scholarship of M. E. Di Pietro. Moreover, G. Celebre, G. De Luca and M. E. Di Pietro
thank University of Calabria and MIUR PRIN 2009 for financial support.
Inducing topological defects by curvature and edges for tunable
colloidal assembly in nematic liquid crystals.
Francesca Serra 1,2, Yimin Luo 2, Yu Xia 3, Mohamed-Amine Gharbi
Shu Yang 3, Kathleen J. Stebe 2
1,2,3
, Randall D. Kamien 1,
1. Department of Physics and Astronomy, University of Pennsylvania, Philadelphia PA 19104
2. Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia PA 19104
3. Laboratory for Research of the Structure of Matter, University of Pennsylvania, Philadelphia PA 19104
e-mail: fraserra@sas.upenn.edu
Topological defects in nematic liquid crystals can be used attract and trap colloids, both in bulk and
at the air-nematic interface [1], and they thus constitute a powerful tool to drive reconfigurable selfassembly. Geometrical cues can be created to control the defects, which are attracted to edges,
corners and regions where high-curvature features are present.
Soft and stretchable membranes with arrays of holes are a promising tool to manipulate the liquid
crystal defects. The pores, initially round, can be either stretched uniaxially or swollen and
deformed during a pattern transformation, similar to that observed in hydrogels [2]. In the pores
deforming from round to oval, the creation of high curvature regions changes the nature and the
position of the topological defects, also inducing a richer variety of defect structures.
This change in the defects, in turn, can be exploited to tune the trapping of colloidal particles, which
are attracted to the poles of the elongated pores. The relative size of pores and particles is another
key parameter that determines the trapping efficiency, thus paving the way to a possible method for
particle sorting.
Figure 1. a-b) Defect structure in a round (a) and elongated pore (b). c) Colloids trapped near the poles of the elongated pores.
Scale-bar is 10 microns.
References
[1] M.Cavallaro Jr, M.A. Gharbi, D.A. Beller, S. Čopar, Z. Shi, T. Baumgart, S. Yang, R.D. Kamien, K.J. Stebe, PNAS
DOI: 10.1073/pnas.1313551110, 2013.
[2] G. Wu, Y. Xia, S. Yang, Soft Matter, vol. 10, 1392–1399, 2014.
Electrical response of a confined isotropic liquid sample:
biological systems and liquid crystals applications
R. R. Ribeiro de Almeida,1,4,5 F. S. Michels,1 V. Steffen,1,2 E. K. Lenzi,1 R. S. Zola,1,3
and L. R. Evangelista.1,*
1 Departamento de Física, Universidade Estadual de Maringá,
Avenida Colombo, 5790 – 87020-900 Maringá, Paraná, Brazil.
2 Departamento de Engenharia Química, Universidade Estadual de Maringá.
Avenida Colombo, 5790 – 87020-900 Maringá, Paraná, Brazil.
3 Universidade Tecnológica Federal do Paraná – Campus Apucarana, Rua Marcílio Dias, 635 – 86812-460,
Apucarana, Paraná, Brazil.
4 Liquid Crystals Institute, Kent State University, P. O. Box 5190, Kent, OH 44242-0001, United States.
5 Capes Fondation, Ministry of Education of Brazil, Brasília, DF 70040-020, Brazil.
In a liquid, among the several origins the macroscopic polarization related to an applied field
may have, the ionic one stands out, which has special importance for living cells [1]. Monitoring
the effective concentration of ions in a living cell is informative about transporters and the
actions of the channels in a cell membrane [2]. The interplay between the existence of
electrochemical forces, such as the adsorption phenomena involved in the molecular trapping
and transport at biomembranes (or at the interface electrode-electrolyte), and external electric
fields is responsible for several effects on the ionic distribution in a liquid medium. In biology,
this interplay is used in physiological studies of ion-selectivity microelectrodes [2] or even for
DNA separation by electrophoresis [3]. These ions diffuse around the cell and an internal
electric field distribution across the sample arises. Interestingly, due to the structural
resemblance with liquid crystals, studying the diffusion of ions in biological materials and its
electrochemical effects has direct application in electro-optical devices made with liquid crystal
materials. The asymmetry in the electric field distribution that results when an applied field is
combined with the internal field in the charge layer has been used as the mechanism to explain
the DC switching of a liquid crystal display [3], many times related to low VHR and image
sticking issues. In this work, the dynamical behavior of ions in electrolytic solutions subjected to
time dependent external voltage of arbitrary shape is analytically investigated in the framework
of the continuum Poisson-Nernst-Planck (PNP) diffusional model. Two different continuity
equations have to be solved, assuming there are positive and negative mobile ions in the
medium, coupled to the Poisson’s equation governing the electrical potential across the sample.
The PNP diffusion model is usually employed for the analysis of the structure and charging
kinetics of electrical double layers at interfaces of electrochemical cells under conditions
relevant to typical engineering applications. Moreover, these calculations are specially important
for recreating the behavior of living cells where, for example, voltage-gated calcium channels
respond to membrane depolarization causing potential changes, which means the electrical
potential is altered with time depending on the cell’s needs [4,5].
References:
[1] H. Pauly and H. P. Schwan, Biophys. J. 6, 621 (1966).
[2] S. -K. Lee, W. F. Boron, and M. D. Parker, Sensors 13, 984 (2013).
[3] R. N. Thurston, J. Cheng, R. B. Meyer, and G. D. Boyd, J. Appl. Phys. 56, 264 (1984).
[4] B. Eisenberg, Biophys. J. 104, 1849 (2013).
[5] R. R. Ribeiro de Almeida et al., Chem. Phys. Lett. 588, 87 (2013).
_____________________________________________
* presenting author; E-mail: lre@dfi.uem.br
Azo-dendrimer for Manipulating Microparticles
3
P. Hirankittiwong1,2, N. Chattham1,2, O. Haba3, K. Yonetake
, A. Eremin1, R. Stannarius1,
1,4,*
and H. Takezoe
1. Department of Nonlinear Phenomena, Institute for Experimental Physics, Otto-von-Guericke-Universität Magdeburg,
Magdeburg, Germany
2. Department of Physics, Faculty of Science, Kasetsart University, Bangkok, Thailand
3. Organic Device Engineering, Yamagata University, Yonezawa, Japan
4. Department of Organic and Polymeric Materials, Tokyo Institute of Technology, Tokyo, Japan
e-mail: takezoe.h.aa@m.titech.ac.jp
Liquid crystal (LC) orientation is specified by interfaces giving an anchoring condition, and is
varied by external stimuli such as electric, magnetic, and optical fields. Here, we introduce azodendrimer molecules, which spontaneously attach to the interfaces and act as a command surface.
Momoi et al. [1] showed that the polyimide-free vertical alignment (VA) for display application can
be achieved just by dissolving poly(propyleneimine)-based LC dendrimers [2] in a nematic LC
(NLC) mixture. Dendritic azobenzene derivatives (azo-dendrimer) [3] are more interesting, since
optical surface manipulation (command surface) is possible through photo-induced trans-to-cis
isomerization. Actually, some of the present authors have already reported the usefulness of the
azo-dendrimer for optical devices [4,5]. In the last decades much attention has been devoted to the
study of micro-/nano-sized particles, particularly for optically controlling or manipulating the
structures for new applications. Here, we report two new systems for azo-dendrimer application; (1)
microspheres in nematic matrix and (2) microrods in nematic matrix. In both systems, the azodendrimers are spontaneously adsorbed at the interfaces between the particles and the matrix just by
dissolving a small amount of dendrimer (0.1-0.3 wt%) into NLC materials.
It is well known that many kinds of topological defects, such as hyperbolic hedgehog defects,
Saturn rings, and boojums, emerge around a microparticle situated in an oriented NLC field. The
manipulation of such defect structures is possible by applying an electric or magnetic fields.
However, the surface molecular manipulation cannot be made using such field application. In our
present system, the surface molecular orientation can be changed between perpendicular and
parallel with respect to the interface by on and off of the UV irradiation. In our system (1), we
originally observed a hedgehog defect or a Saturn ring perpendicular to the rubbing direction. Upon
UV irradiation, the defect structure changes to a boojum because of the anchoring condition change
in the particle surface by UV light irradiation. Our system (2) is more interesting. Depending on the
angle of rod with respect to the nematic director field, the local director fields around the rod are
mirror symmetric or inversion symmetric, which induce the preferential reorientation of surface LC
molecules upon trans to cis photoisomerization. This triggers dynamic motion of rods such as
rotation and translation. We will show real-time movies of such dynamic motions.
References
[1] K. Yonetake, T. Masuko, T. Morishita, K. Suzuki, M. Ueda, and R. Nagahata, “Poly(propyleneimine)dendrimers
peripherally modified with mesogens”, Macromolecules vol. 32, p. 6578, 1999.
[2] Y. Momoi, M. Kwak, D. Choi, Y. Choi, K. Jeong, T. Koda, O. Haba, K. Yonetake, “Polyimide-free LCD by
dissolving dendrimers”, J. Soc. Inf. Display vol. 20, p. 486, 2012.
[3] W. Li, T. Dohi, M. Hara, S. Nagano, O. Haba, K. Yonetake, T. Seki, “Phototriggered mass migration consorted
with surface dewetting in thin films of a liquid crystalline azobenzene-containing dendrimer”, Macromolecules
vol. 45, p. 6618, 2012.
[4] T. Ikeda, S. Aya, F. Araoka, K. Ishikawa, O. Haba, K. Yonetake, Y. Momoi, and H. Takezoe, “Novel Bistable
Device Using Anchoring Transition and Command Surface”, Appl. Phys. Exp. vol. 6, p. 061701, 2013.
[5] G. Lee, F. Araoka, K. Ishikawa, Y. Momoi, O. Haba, K. Yonetake, and H. Takezoe, “Photo-induced ordering
transition in microdroplets of liquid crystals with azo-dendrimer”, Part. Part. Syst. Charact. vol. 30, p.847, 2013.
Molecular organisation in nematic liquid crystals close to a solid
surface
Otello M. Roscioni 1*, Antonio Pizzirusso1, Luca Muccioli 1, Claudio Zannoni1
1.
Dipartimento di Chimica Industriale “Toso Montanari”, Università di Bologna, viale Risorgimento 4, 40136
Bologna, Italy
*e-mail: otellomaria.roscioni@unibo.it
Many phenomena take place at the interface between two or more materials. For instance, in
organic field-effect transistors, the first few molecular layers of the semiconductor supported on a
dielectric substrate account almost entirely for the macroscopic drain-source current of the resulting
device [1]. In addition to that, the charge transport is also affected by the morphology and the
molecular packing of the active layer. In Liquid Crystal Displays (LCD) surface alignment of the
mesogens and anchoring is a key property, still treated in an empirical way that has not, until very
recently, been predicted by modelling and computer simulations [2].
Given the importance that surfaces have in affecting the properties of an overlying material, we
present here a detailed characterisation of the morphology and structural properties of a common
nematic liquid crystal (LC), 5CB, supported over various substrates of technological significance
[2,3]. We modelled the LC/substrate interface with atomistic molecular dynamics simulations, and
found that the surface ordering of the LC is influenced by the magnitude of the anchoring energy
and the morphology of the substrate. We found that the molecular organisation of the LC changes in
response to the chemical composition of the surface, its morphology and roughness. The predicting
power of the present methodology allows us to determine the molecular organisation of a given
material without any a priori knowledge, as it is based only on the accurate representation of its
components.
Figure 1. Lateral view of two films of 2000 5CB molecules supported on crystal and amorphous SiO2 at 300K. Molecules are
colour coded according to their orientation with respect to the surface, ranging from blue (perpendicular) to white (parallel).
References
[1] A. Shehu, S. D. Quiroga, P. D’Angelo, C. Albonetti, F. Borgatti, M. Murgia, A. Scorzoni, P. Stoliar, F.
Biscarini. “Layered Distribution of Charge Carriers in Organic Thin Film Transistors”. Phys. Rev. Lett.
104, 246602 (2010).
[2] A. Pizzirusso, R. Berardi, L. Muccioli, M. Ricci, C. Zannoni. “Predicting surface anchoring: molecular
organization across a thin film of 5CB liquid crystal on silicon”, Chem. Sci., 3, 573-579 (2012).
[3] O. M. Roscioni, O. M. Roscioni, L. Muccioli, R. G. Della Valle, A. Pizzirusso, M. Ricci, C. Zannoni.
“Predicting the anchoring of liquid crystals at a solid surface: 5-cyanobiphenyl on cristobalite and glassy
silica surfaces of increasing roughness”, Langmuir, 29, 8950-8958 (2013).
Acknowledgment: We thank EU project MINOTOR (grant no.FP7-NMP-228424) for funding and the CINECA
Supercomputing Centre for computer time through an ISCRA grant.
Visual micro-thermometers for nanoparticles photo-thermal conversion
Gia Petriashvili1,2, Maria P. De Santo1, Ketevan Chubinidze3,
Ridha Hamdi4 and Riccardo Barberi1,*
1 Physics Department and IPCF-CNR UOS Cosenza, University of Calabria, Cosenza, Italy
2 Institute of Cybernetics of the Georgian Technical University, Tbilisi, Georgia
3 Tbilisi State University, Tbilisi, Georgia
4Physics Laboratory of Soft Matter and Electromagnetic Modelling, Faculty of Sciences of Tunis, University of Tunis
El Manar, Tunis, Tunisia
We present a novel method to calibrate the light to heat conversion in an aqueous fluid containing
nanoparticles. Accurate control of light and heat is of dramatic importance in many fields of science
and metal nanoparticles have acquired an increased importance as means to address heat in very
small areas when irradiated with an intense light[1,2]. The proposed method enables to measure the
temperature in the environment surrounding nanoparticles, as a function of the exposure time to
laser radiation, exploiting the properties of thermochromic cholesteric liquid crystals[3]. This
method overcomes the problems of miscibility of nanoparticles in liquid crystals, provides
temperature reading at the microscale, since the cholesteric liquid crystal is confined in
microdroplets, and it is sensitive to a temperature variation, 28°C-49°C, suitable for biological
applications.
In the figure below the colored trace left in the material after switching off the laser beam is shown.
References
[1] A. O. Govorov, H. H. Richardson, Nano Today 2, 30-38 (2007).
[2] G. Baffou, R. Quidant, Laser Photon. Rev. 7, 171–187 (2013).
[3] Parsley M, Handbook of thermochromic liquid crystal technology, Hallcrest, Glenview, (1991).
Optical trapping of chiral microresonator
A. Mazzulla1, M. G. Donato2, J. Hernandez3, Clementina Provenzano3, R. Saija4, R. Sayed2,4, S.
Vasi2,4, A. Magazzù2,4, P. Pagliusi1,3, R. Bartolino1,3,5, P. G. Gucciardi2, O. M. Maragò2 and G.
Cipparrone1,3
1. CNR-IPCF, UOS Cosenza, Ponte P. Bucci, Cubo 33B, 87036 Rende (CS), Italy
2. CNR-IPCF, Istituto per i Processi Chimico-Fisici, I-98158 Messina, Italy.
3. Physics Department, University of Calabria, Ponte P. Bucci, Cubo 33B, 87036 Rende (CS), Italy
4. Dipartimento di Fisica e Scienze della Terra, Università di Messina, Messina, Italy
5. Centro Interdisciplinare “B. Segre” dell’Accademia Nazionale dei Lincei, Roma, Italy
e-mail: alfredo.mazzulla@cnr.it
We perform experimental and theoretical investigations of the simultaneous optical trapping and
rotation of spherulite-like chiral microparticles [1,2]. The coupling of linear and angular
momentum, mediated by the light spin and the microparticles chiral reflective properties, allows for
fine tuning of chirality-induced optical forces and torques. The outcomes offer novel tools for
optomechanics, optical sorting and sensing, and optofluidics.
Figure 1. Chiral microresonators. (a) Reflection R+ from a chiral layer with pitch p and variable thickness, d. (b)
Transmission spectrum of a CLC film between two glass substrates with planar texture for linearly polarized light. (c) Sketch of a
polymeric particle with spherulite-like configuration of the helical structure. (d) Optical microscope image of the particle between
crossed polarizers. (e) SEM image of a half particle showing the “onion-like” structure.
References
[1] M. G. Donato, J Hernandez, A. Mazzulla, C Provenzano, R Saija, R Sayed, S Vasi, A Magazzù, P Pagliusi, R
Bartolino, P G Gucciardi, O M Maragò, G Cipparrone, "Polarization-dependent optomechanics mediated by chiral
microresonators", Nature Communications, vol. 5, 3656, 2014. ISSN: 2041-1723, DOI: 10.1038/ncomms4656
[2] R.J. Hernández, A. Mazzulla, A. Pane, K. Volke-Sepulveda, G. Cipparrone, "Attractive-repulsive dynamics on
light-responsive chiral microparticles induced by polarized tweezers", LAB ON A CHIP, vol. 13, 459-467, 2013.
ISSN: 1473-0197, DOI: 10.1039/C2LC40703E
Acknowledgment: We acknowledge Progetto di Grande Rilevanza Italia Messico 2011-2013 (MAE) and MPNS COST
Action 1205 ‘Advances in Optofluidics: Integration of Optical Control and Photonics with Micro-fluidics’ for support.
Ellipsometric study of nematic alignment
on Silicon Oxides for displays
A. Marino1, E. Oton2, N. Bennis3, X. Quintana2, J. M. Oton2, V. Tkachenko1
1. National Research Council, CNR-SPIN, Physical Sciences Department, University of Naples Federico II,
Via Cintia Monte S.Angelo, 80126 Naples, Italy
2. CEMDATIC, ETSI Telecomunicación, Universidad Politécnica de Madrid,
Avda. Complutense s/n, 28040 Madrid, Spain
3. Institute of Applied Physics, Military University of Technology,
Warsaw, Poland
e-mail: antigone.marino@spin.cnr.it
Vertical Alignment Nematics (VANs) displays are a form of LCDs in which the liquid crystals
naturally align vertically to the glass substrates. In spite of their name, the liquid crystal (LC)
director is never exactly vertical, rather it always show a small angle with the normal to the sample
plane called tilt that may vary throughout the cell bulk. Its values are ultimately determined by the
pretilt, defined as the tilt angle on the surfaces in the absence of voltage. The control of tilt angle
distribution inside VAN LC thin films is essential for many applications [1]. Higher pretilts lead to
faster displays, because the delay time of the dynamic response decreases. However, increasing the
pretilt the quality of the dark state is reduced, for birefringence of the off state increases
accordingly. Thus a delicate balance between delay time and contrast has to be sought in the
manufacturing of VAN displays. A fine control of the pretilt is crucial for VAN displays
performance optimization.
With this aim, we have investigated, by means of variable angle spectroscopic ellipsometry, the
pretilt angle in silicon oxides alignment surfaces, focusing on SiOx and SiO2. Those vertical
alignment layers had been realized by thermal evaporation. Changing the deposition angle it is
possible to control the pretilt angle. The director profile inside the sample was inferred by reflection
and transmission ellipsometric measurements.
Pretilt measurements were made using an ellipsometric technique, based on recording changes in
the state of polarization when a beam light impinges the surface [2]. This technique allowed
measuring pretilt angle of the liquid crystal molecules placed next to the SiOx or SiO2 surfaces with
more accuracy than on typical methods (especially for very low pretilt angles). The full comparative
study of VANs pretilt angles on SiOx and SiO2 layers and their influence over electrooptic
response will be presented.
References
[1] D. Armitage, I. Underwood, and S. T. Wu, “Introduction to Microdisplay”, Wiley, New York, (2006).
[2] A. Marino, E. Santamato, N. Bennis, X. Quintana, J.M. Otón, V. Tkachenko, G. Abbate, “Ellipsometric study of
vertically aligned nematic liquid crystals” App. Phys. Lett. 94 013508 (2009).
Plasmonic nano-heaters confined in self-organized materials
Giovanna Palermo1*, Luciano De Sio1, 2, Tiziana Placido3,4, Roberto Comparelli4,
Maria Lucia Curri4, Nelson Tabiryan2, Cesare Umeton1,5,
Roberto Bartolino1, 5, 6, Timothy Bunning7
1
Department of Physics - University of Calabria Centre of Excellence for the Study of Innovative Functional Materials 87036 Arcavacata di Rende,
Italy
2
Beam Engineering for Advanced Measurements Company, Winter Park, Florida 32789, USA
3
4
Università degli Studi di Bari – Dip. Chimica, Via Orabona 4, 70126 - Bari, Italy
CNR-IPCF Istituto per i Processi Chimici e Fisici, Sez. Bari, c/o Dip. Chimica Via Orabona 4, 70126 - Bari, Italy
5
CNR-IPCF UOS Cosenza - 87036 Arcavacata di Rende, Italy
6
Centro Linceo of the National Academy dei Lincei, Rome
7
Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio 45433-7707, USA
*Corresponding author: giovanna.palermo@fis.unical.it
Localized plasmon resonance (LPR) of noble metal nanoparticles (MNPs) opens up a new horizon
for nanoscale conversion of light into heat. Due to the electron-electron scattering and the electronphonon coupling associated with the LPR effect, the strong electric field generated around the
MNPs is converted into heat and the MNPs behave as nanosources of heat. An important challenge
is represented by the ability of measuring temperature variation at the surface of the MNPs under
optical illumination, since the nano-localized the temperature variation is the most important
parameter for applications ranging from nanomedicine to photonics. Investigation of the heat
transport mechanism, from the heated MNPs to their surrounding medium, is a fundamental step in
realizing nano-localized sources of heat for applications in nanotechnology and thermal-based
therapies. In this framework, we have advanced a breakthrough in monitoring nanoscale
temperature variations by combining capabilities of short pitch liquid crystalline compounds and
MNPs. In particular, we have shown that a very interesting class of NPs is represented by gold
nanorods (GNRs) which have two LPRs, namely transverse and longitudinal, which can be
promptly tuned from visible to NIR, by changing the particle geometry [1]. By exploiting the
selective reflection of the cholesteric liquid crystal, we have developed [2, 3, 4] a nanoscale
thermometer suitable for real time and high sensitivity measurement of the localized temperature
around GNRs under a suitable (resonant) and water transparent (NIR) optical illumination.
References
[1] L. De Sio, Active Plasmonic Nanomaterials. Pan Stanford Publishing, Singapore, 2014 (in press)
[2] L. De Sio, T. Placido, S. Serak, R. Comparelli, M. Tamborra, N. Tabiryan, L. Curri, R. Bartolino, C. Umeton, T.
Bunning “Nano-Localized Heating Source for Photonics and Plasmonics” Advanced Optical Materials 2013, 1(12),
992. Paper include also the back cover picture of the journal. Paper has been included in 12 outstanding articles
published in Advanced Optical Materials in 2013.
[3] L. De Sio, T. Placido, R. Comparelli, L. Curri, N. Tabiryan, T. Bunning “ Thermo-plasmonics in self-organized
materials” Nanotech 2014 (in press)
[4] L. De Sio, T. Placido, G. Palermo, R. Comparelli, N. Tabiryan, L. Curri, C. Umeton, R. Bartolino, T. Bunning
“Generating heat with plasmonic nanoparticles: from photoswitching to phototuning” 2014 (submitted).
Acknowledgements
The research is supported by the Air Force Office of Scientific Research (AFOSR), Air Force Research Laboratory (AFRL), U.S.
Air Force, under grant FA9550-14-1-0050 (P.I. L. De Sio, EOARD 2014/2015) and the Materials and Manufacturing Directorate,
AFRL; by the EC-funded project METACHEM (Grant CP-FP 228762-2) and by PRIN 2010-2011 - prot. 2010C4R8M8.
Alignment of chromonic molecules
Caterina M.Tone 1, Maria P.De Santo1,2, Federica Ciuchi2
1. Phys.Dept. Università della Calabria 87036 Rende
2. IPCF UOS Cosenza c/o Phys.Dept. Università della Calabria 87036 Rende
We report our latest studies on the alignment of chromonic liquid crystals, a special class of
molecules which recently attracted the attention of researchers especially for their biocompatibility.
Lyotropic Chromonic Liquid Crystals (LCLCs) are water-based systems consisting of planar
molecules, that present either a nematic phase and a two-dimensional crystalline order (columnar
phase) increasing the concentration.
We focused our attention on the alignment of the liquid crystals phases of two chromonic
compounds: disodium cromoglycate (DSCG) and guanosine derivatives.
Nematic phase of the first compound was aligned in both planar and hometropic configurations
exploiting the surface properties of the alignment layers. We tested hydrophilic and hydrophobic
amorphous surfaces obtaining stable-in-time alignments.
For guanosine derivatives LC phases, the planar alignment was generally hindered by surface
morphology (for amorphous substrates) or by the formation of superstructures in solution, that were
partially aligned on a scale of 20microns.
A stable in time homeotropic alignment of guanosine LC phases has been obtained using the
surface properties of the alignment layer, without the application of an external field. However,
according to the concentration and/or the addition of salts to guanosine LC solution, the
homeotropic alignment coexisted with the presence of metastable guanosine vesicles.
In both cases, the alignment behaviour was influenced by the addition of salts and concentration of
guanosine in solution.
References
[1] C.M. Tone, M.P. De Santo, M.G. Buonomenna, G.Golemme and F.Ciuchi “Dinamical homeotropic and planar
alignment of chromonic liquid crystals” Soft Matter DOI:10.1039/c2sm26021b vol. 8 (32) , 8478-8482, 2012.
[2] C. M. Tone, M. P. De Santo, F. Ciuchi "The role of surface energy in guanosine nucleotide alignment: an intriguing
scenario" accepted for publication in Colloids and Surfaces B: Biointerfaces 10.1016/j.colsurfb.2014.04.004.
Acknowledgment:
C.M. Tone wishes to acknowledge the European Commission, European Social Fund and Regione Calabria, (POR)
Calabria - FSE 2007/2013 obiettivo M2 for financial support.
Order reconstruction in turbulent nematics
Giuseppe Pucci1, Francesco Carbone2, Giuseppe Lombardo2, Carlo Versace1 and
Riccardo Barberi1,2
1. Dipartimento di Fisica, Università della Calabria, Ponte Pietro Bucci 31C, I-87036 Rende (CS), Italy
2. CNR-IPCF UOS di Cosenza, c/o Università della Calabria, I-87036 Rende, (CS), Italy
e-mail: giuseppe.pucci@fis.unical.it
Calamitic nematics are usually described in terms of uniaxial order. Experiencing strong
frustrations, they undergo a uniaxial to biaxial order transition known as order reconstruction,
which has been largely investigated for quasi-static systems [1,2]. We present two experimental
evidences that order reconstruction is the process responsible for defect generation at the transition
occurring in the turbulent electro-hydrodynamics of nematics. In contrast to isotropic fluids, highly
forced turbulent nematics present a transition between two regimes, known as Dynamic Scattering
Mode 1 (DSM1) and Dynamic Scattering Mode 2 (DSM2) because they strongly scatters light [3].
DSM2 is characterized by high density of topological defects. First, we show how to control the
transition threshold by varying the material biaxial coherence length. Second, we report
observations of changes of textural topology due to the transition, which we visualize through the
orientation of Kapustin-Williams stripes [fig.1].
Finally, we show a novel transition obtained in an analogous system leading to the suppression of
turbulence. The transition occurs as an asymmetric nucleation, where nuclei expand through the
propagation of a defect line. As in the DSM1-DSM2 one, this transition leads to changes of textural
topology that we show using again the stripe orientation technique.
Figure 1. Two different topologies observed as a result of the DSM1-DSM2 transition. (a, b) Relaxation of a region in which
DSM2 was developed (crossed polarizers). (c) Kapustin-Williams stripes perpendicular to each other showing the existence of a πtwisted configuration. Cell thickness d=100µm. Voltage switched-off at t=0s. (d) Strip of paper stuck at its ends as an analogue of
order reconstruction. If the strip is cut in two parts, then one part is twisted and reconnected to the other, the whole strip will be
twisted. The strip will never recover the initial configuration by simple elastic deformations. Order reconstruction plays the role of
cutting and reconnecting the strip, while a disclination can be thought as the part of the strip at which the order reconstruction occurs.
References
[1] R. Barberi, F. Ciuchi, G. Lombardo, Bartolino, R., Durand G. E. Time Resolved Experimental Analysis of the
Electric Field Induced Biaxial Order Reconstruction in Nematics. Phys. Rev. Lett. 93, 13 (2004).
[2] G. Lombardo, H. Ayeb, R. Barberi, “Dynamical Q-tensor model description of biaxial nematic order reconstruction
phenomena”, Phys. Rev. E 77, 05178 (2008).
[3] S. Kai, W. Zimmermann, M. Andoh, N. Chizumi, “Local transition to turbulence in electrohydrodynamic
convection”, Phys. Rev. Lett. 64, 1111 (1990).
Translational Self-Diffusion in Liquid Crystals by means of NMR
Diffusometry: Recent advancements
Mario Cifelli 1, Valentina Domenici1, Sergey V. Dvinskikh 2
1. Dipartimento di Chimica e Chimica Industriale, Università degli studi di Pisa, Via Risorgimento 35, 56126, PISA,
Italy
2. Royal Institute of Technology, Department of Chemistry, Teknikringen 36, SE-10044 Stockholm, Sweden
NMR diffusometry[1] is nowadays a well established technique to investigate translational
diffusion processes in thermotropic liquid crystalline phases[2] and recently, the diffusional
behaviour of chiral smectic phases with different clinicity, such as the ferroelectric and
antiferroelectric has been successfully measured[3,4]. In this presentation we report novel
investigations of translational self-diffusion in smectic phases formed by ionic liquid mesogens
based on 1dodecyl-3-metyhl-imidazolium cation (C12-MIM) with two different counter ions (C12MIMCl and C12-MIMBF4) and nematic phases of a 1,3,4 oxadiazole-based bent-core nematogen
[5].
References
[1] W.S: Price, “Pulsed-Field Gradient Nuclear Magnetic Resonance as a Tool for Studying Translational Diffusion:
Part 1. Basic Theory”, Concepts Magn. Reson., vol. 9, 299-336, 1997.
[2] S.V. Dvinskikh, I. Furó, “Nuclear magnetic resonance studies of translational diffusion in thermotropic liquid
crystals” Russ. Chem. Rev., vol. 75, 497-506, 2006.
[3] M. Cifelli, V. Domenici, S.V. Dvinskikh, M. Glogarova, C.A. Veracini, “Translational self-diffusion in the synclinic
to anticlinic phases of a ferroelectric liquid crystal”, Soft Matter, vol. 6, pp 5999-6003, 2010
[4] M. Cifelli, V. Domenici, S.V. Dvinskikh, C.A. Veracini, H. Zimmermann, “Translational Self-Diffusion in the
Smectic Phases of Ferroelectric Liquid Crystals: an Overview”, Phase Transitions, vol. 85, 861-871, 2012.
[5] F. Speetjens, J. Lindborg, T. Tauscher, N. LaFemina, J. Nguyen, E.T. Samulski, F. Vita, O. Francescangeli, E.
Scharrer, “Low nematic onset temperatures and room temperature cybotactic behavior in 1,3,4 oxadiazole-based bentcore mesogens possessing lateral methyl groups” J. Mater. Chem., vol. 22, 22558-22564, 2012.
Acknowledgment: This work has been supported by the Swedish Research Council. Authors are also grateful to Dr. G.
Saielli for providing the ionic LC samples, Prof. O. Francescangeli for providing 2MePh(mono2MeODBP) mesogen
and to Prof. I. Furó for helpful discussion.
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