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Crystalline systems and gels (568-573)
COLL
568: Conservative and dissipative structures in
colloidal dispersions in an electric field
Tsuneo Okubo, Department of Applied Chemistry, Gifu University,
Yanagido 1-1, Gifu 501-1193, Japan, Fax: 81-58-293-2628, okubotsu@apchem.gifu-u.ac.jp
Abstract
The lattice structure, crystal size, structural relaxation time, diffusion
coefficient, melting temperature, critical sphere concentration of
melting, elastic modulus, viscosity, visco-elasticity and other properties
of giant colloidal crystals were studied. Crystallization takes place by
the Brownian movement of colloidal spheres and by their electrostatic
inter-sphere repulsion. Crystal growth processes were quite similar to
those of other crystal systems. Electro-optic effects of colloidal
crystals, which are essential to make new type of electro-optic devices
and photonic crystals have been studied in detail. Phase difference,
second-order and higher order harmonics, synchronous oscillation and
further the existence of a characteristic frequency were clarified for
colloidal crystals. Dissipative patterns formed in the course of drying
the colloidal crystals on a cover glass were studied. Spoke-like,
ring-like and broad ring-like patterns were formed on macroscopic scale.
Fractal patterns were observed on microscopic scale. The dissipative
patterns were also studied in an electric field.
COLL
569: Linear and nonlinear electro-optic response
of chiral smectic liquid crystals
Yasuyuki Kimura, and Reinosuke Hayakawa, Department of Applied
Physics, School of Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku,
Tokyo 113-8656, Japan, Fax: +81-3-5841-6853, kimura@exp.t.u-tokyo.ac.jp
Abstract
Electrooptical measurement is one of useful methods to Electrooptical
measurement is one of useful methods to study dynamical response of liquid
crystals. Compared to dielectric spectroscopy, electrooptical spectroscopy
is less influenced by dc conductivity of the sample and is applicable to
measurements in greater variety of cell configurations. In this study, we
have studied the linear and nonlinear electrooptical relaxation spectra of
ferroelectric liquid crystals (FLCs) and antiferroelectric liquid crystals
(AFLCs). In FLCs, the obtained linear spectrum shows a Debye-type
relaxation corresponding to a ferroelectric Goldstone mode, and the
nonlinear spectra of second and third-order exhibit extended forms of
Debye-type to nonlinear case. In AFLCs, a second-order nonlinear spectrum
shows a Debye-type spectrum corresponding to an antiferroelectric
Goldstone mode, which is not observed in a linear spectrum. Theoretical
calculation shows that the linear and third-order nonlinear components
relate changes in an apparent optical axis and the second-order one
relates changes in birefringence induced by an electric field.
COLL
570: Scattering study of topological gel
Kohzo Ito, and Yasushi Okumura, Graduate School of Frontier
Sciences, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 116-8656, Japan,
Fax: +81-3-5841-8738, kohzo@k.u-tokyo.ac.jp
Abstract
We have recently developed a novel kind of gel, i.e., topological gel,
which has figure-of-eight cross-links freely moving in a polymer network.
In the topological gel, the polymer chains with bulky end groups are
neither covalently cross-linked like in chemical gels nor attractively
interacted like in physical gels, but are topologically interlocked by
figure-of-eight cross-links. It is therefore expected that the
figure-of-eight cross-links can pass the polymer chains freely to equalize
the "tension" of the threading polymer chains just like pulleys.
Therefore, the nanoscopic heterogeneity in structure and stress should be
automatically equalized in the gel. Actually we have investigated the
topological gel by using neutron scattering under mechanical deformation
and by dynamic light scattering. The experimental results clearly
indicated that the figure-of-eight cross-links moved in the network.
COLL
571: Colloidal crystallization of polymer-modified
silica in organic solvents and immobilization by gelation
Kohji Yoshinaga, and Kumiko Fujiwara, Department of Applied
Chemistry, Kyushu Institute of Technology, Sensui 1, Tobata, Kitakyushu,
Fukuoka 804-8550, Japan, Fax: +81-93-884-3316, khyosina@che.kyutech.ac.jp
Abstract
Colloidal crystallization of polymer-modified colloidal silica (136 nm) in
organic solvents and its immobilization by gelation with radical
polymerization were investigated. The crystallization was observed in
organic solvent, which was a good solvent for modified polymer. It was
also observed that there was matching or mismatching of modified polymer
and solvent for the crystallization. The radical copolymerization of
methyl methacrylate and the macromonomer in the colloidal crystals of
poly(methyl methacrylate)/SiO2 in CH3CN brought
about gelation, but colloidal crystals disappeared. Gelation by using
divinyl monomer instead of macromonomer led to immobilization of the
crystals. Reflection spectra of the crystal-immobilized gel showed that
particle-arrays of the front side of the gel differed from the rear side,
and it depended on the polymerization rate and the amount of cross-linker.
Immobilization of the colloidal crystals was successfully achieved by
lowering of optical path for gelation, and by decreasing of radical
initiator and the cross-linker.
COLL
572: Intra- and interparticle interactions of
polyampholyte nanogels
Etsuo Kokufuta, Atsushi Nakayama, and Kazuyoshi Ogawa, Institute of
Applied Biochemistry, University of Tsukuba, Tsukuba, Ibaraki 305-8565,
Japan, Fax: +81-298-53-4605, kokufuta@sakura.cc.tsukuba.ac.jp
Abstract
Nano-sized polyampholyte gel particles were synthesized by aqueous redox
polymerization in the presence of sodium dodecylbenzene sulfonate as a
surfactant. Acrylic acid and 1-vinylimidazole were respectively used as an
anionic and a cationic monomer, both of which were incorporated into the
network of N-isopropylacrylamide cross-linked with
N,N'-methylenebisacrylamide. The intra- and interparticle interactions
were studied as a function of pH, ionic strength and temperature by static
and dynamic light scattering, electrophoretic light scattering and
turbidity measurements. Hydrodynamic radius of particles became minimum at
the pH corresponding to an isoelectric point (pI). At pH=pI the particle
swelled upon addition of salt such as NaCl, indicating antipolyelectrolyte
behavior. In addition to these size changes due to intraparticle
interaction, aqueous nanogel dispersions underwent a shape phase
separation due to interparticle interaction when pH and salt concentration
were varied.
COLL
573: Unusual electro-optical effects and molecular
properties of novel LC polymers with siloxane main-chain and laterally
attached cyanobiphenylene mesogenic side groups
Peter Lavrenko1, Olga Okatova1, Igor
Kolomiets2, David Lacey3, and Alan W. Hall3.
(1) Institute of Macromolecular Compounds, Russian Academy of Sciences,
Bolshoy pr., 31, 199004, Saint-Petersburg, Russia, Fax: 7 (812) 328-6869,
lavrenko@mail.macro.ru, (2) Institute of Physics, St.-Petersburg State
University, (3) Department of Chemistry, The University of Hull
Abstract
We have investigated three novel liquid crystalline polymers with the
cyanobiphenylene mesogenic side groups laterally attached to the siloxane
main chain via -(CH2)k- (k=5 to 11) spacers with the
electrooptical Kerr effect and molecular hydrodynamics methods in
solutions. Optical and conformational properties will be presented as well
as parameters of orientational mobility of the mesogenic groups which will
be compared with those of a suitable low molecular weight compound.
Correlations will be analyzed between the type of the mesophase and the
chemical structure of the molecule. Origins of the unusual relaxation
behavior of the polymers will be also discussed.
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