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Poster session (188-199)
COLL
188: CdS quantum dots prepared via electroporation of vesicles:
Experimental and computational results
Honxia Zeng, Dennis S. Marynick, and Zoltan A. Schelly, Center for
Colloidal and Interfacial Dynamics, University of Texas at Arlington,
Department of Chemistry and Biochemistry, Arlington, TX 76019-0065,
zenghx1116@yahoo.com
Abstract
Ultra small CdS quantum dots (8 to 20 Å diameter, according to TEM) were
prepared via electroporation of synthetic, unilamellar DOPC vesicles (<Dh>=175
nm). The slow self-aggregation (occurring over several hours) of the CdS
monomers adsorbed on the exterior surface of the vesicles allows for
convenient monitoring of the formation of (CdS)n clusters, and
their transformation to semiconductor quantum dots upon further cluster
growth. Growth in the molecular size range (n=1-4) is associated with a
blue-shift of the UV absorption band, followed by a general red-shift in
the quantum dot size regime. The emergence of the electronic band
structure occurs at the turning point of the spectral band-shift (at n=5).
Results of HOMO-LUMO gap calculations through DFT at B3P86/6-31+G* level,
with full geometry optimization for n=1-6, are in agreement with the
trends in the spectral band-shift observed.
COLL
189: Electro-optics of cylindrical dendrimers
Nikolai V. Tsvetkov, Vera O. Ivanova, Nina V. Girbasova, and Alexey
Yu. Bilibin, Physical Faculty, St. Petersburg State University, 198504,
Ulianovskaya st. 1, St. Petersburg, Petrodvoretz, Russia, N.Tsvetkov@paloma.spbu.ru
Abstract
Molecular characteristics of linear dendrimers of the first (LD-1) and the
second generations (LD-2) obtained on the basis of L-asparagine acid were
investigated over a wide molecular weight (MW) range using the methods of
equilibrium and non-equilibrium electrical birefringence (EB). It was
established that the insertion of bulky side dendrite substitutes does not
cause a considerable change in equilibrium chain rigidity. It was found
that when the generation number of dendrite substitutes is varied, the
character of reorientation of dendronized polymer molecules in electric
fields undergoes fundamental change. The values of equilibrium EB for
polymers under investigation are markedly greater than the corresponding
values for their monomers. The dependence of equilibrium Kerr constant K
on MV of LD-2 makes it possible to obtain the Kuhn segment length A=60 ×
10-8 cm, which is in good agreement with data obtained by
methods of molecular hydrodynamics.
COLL
190: Electro-optical behavior of fullerene-containing
liquid-crystalline dendrimers in solutions
Natalia P. Yevlampieva1, Peter Lavrenko2,
Blaise Dardel3, and Robert Deschenaux3. (1)
Institute of Physics, St. Petersburg State University, Ulianovskaja st. 1,
198504 St. Petersburg, Russia, Fax: 7-812-428-7240, yevlam@paloma.spbu.ru,
(2) Institute of Macromolecular Compounds, Russian Academy of Sciences,
(3) Institute de Chimie, Universite de Neuchatel
Abstract
The synthesis of multifunctional materials performed by multicomponent
single molecules of special chemical architecture is one of the modern
trends in materials science. In the present work, malonate dendrimers have
been used as matrix molecules for the synthesis of novel liquid
crystalline (LC) materials with covalently linked fullerene C60
as additional functional component. Two purposes have been realized in the
molecular design of novel LCs: 1) combination of typical mesogene
compounds as the end groups with dendritic structure of the matrix
molecule, and 2) incorporation of fullerene to LC molecules.
Electrooptical Kerr effect and hydrodynamic methods have been utilized to
study the dendritic samples with a variable fullerene position for
examining the influence of fullerene on the molecular properties of the
original LC dendrimers. It was detected that substituted fullerene C60
reinforces the electrooptical effect of LC dendrimers and only slightly
changes their size and mobility in solution.
COLL
191: Specific electro-optical properties of different type fullerene
C60-poly(vinyl pyrrolydone) derivatives
Natalia P. Yevlampieva1, Olga V. Nazarova2,
Evgenii F. Panarin2, and Evgenii I. Rjumtsev1. (1)
Institute of Physics, St. Petersburg State University, Ulianovskaja st. 1,
198504 St. Petersburg, Russia, Fax: 7-812-428-7240, yevlam@paloma.spbu.ru,
(2) Institute of Macromolecular Compounds, Russian Academy of Sciences
Abstract
Poly(vinylpyrrolydone) (PVP) derivatives of fullerene C60 are
water soluble compounds which can be used for studying the biological
activity of fullerene. In the present work, we have tested electrooptical
properties (Kerr effect in pulsed electric field) in chloroform of PVP-C60
derivatives with a variable linkage type between polymer and fullerene.
Donor-acceptor complexes between PVP and C60 with 1–5 weight
% fullerene were used as examples of the first type of linkage. Another
type chemical linkage was realized by synthesis of star-like PVP-C60
samples with the PVP-arms covalently bonded to the fullerene core by means
of terminal amino-groups. The behavior of PVP-C60 samples with
covalently linked fullerene was found to radically differ from that of the
initial PVP and complex-type samples: difference in sign and magnitude of
the electrooptical effect was observed. The predominant role of the state
of fullerene was declared as a possible reason of the detected
specificity.
COLL
192: Steady electro-optic parameters in noninteracting colloidal
dispersions
Svetla Miteva, and Maria Stoimenova, Institute of Physical
Chemistry, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria, smiteva@ipc.bas.bg
Abstract
Due to strong light scattering the electro-optic effects in colloids are
strongly dependent on particle concentration even in the case of dilute
(non-interacting) systems. Basic electro-optic parameters like electric
polarizability, permanent dipole moment, particle relaxation time, etc.
are also influenced by this dependence. The paper investigates the
possibility to determine electro-optic parameters which are not influenced
by the optical effects in the system and remain steady with the increase
of particle concentration. The results are illustrated on aqueous
suspensions of monodisperse b-FeOOH
particles in the concentration range 5.10-3 - 5.10-1
g/L where the amplitude of the effects varies from positive 100% to
negative 30% (C* is above 10 g/L).
COLL
193: Magneto-conductometric method of studying colloidal particle's
electric polarizability
Anatoli Spartakov, Anatoli Trusov, and Vladislav Vojtylov,
Department of Physics, St. Petersburg State University, Ulianovskaya 1,
Sankt-Petersburg 198504, Russia, Fax: 07-812-4287240, Anatoli.Trusov@pobox.spbu.ru,
Vladislav.Voitylov@paloma.spbu.ru
Abstract
A new magneto-conductometric method of investigation of colloidal
particle’s polarizability was developed. It is based on the study of
conductivity anisotropy induced in colloids by magnetic field. This
anisotropy is connected with the orientation of non-spherical magnetically
anisotropic particles. The main advantages of this method over
electroorientational one are the following: 1). It permits to study
colloids with considerably high conductivity. 2). This method can be
applied in a wide range of electric field frequencies. The values of
electrical polarizability of different colloidal particles are in good
agreement with data obtained by electroorientational methods. Size and
shape distribution functions required for the correct determination of
polarizability values were determined previously by the electro- or
magnetoorientational methods. Acknowledgment: Authors thank the Russian
Foundation for Fundamental Research (no. 01-03-33253a).
COLL
194: Kerr effect in structured copolymer melts
Sergey G. Polushin, Sergey K. Filippov, Andrey V. Lezov, and Evgeny
I. Rjumtsev, Department of Polymers, Saint-Petersburg State University,
Institute of Physics, Ulianovskaia 1, Saint-Petersburg, Russia, Fax:
812-428-7598, polushin@paloma.spbu.ru
Abstract
Liquid crystalline copolymers containing ionogenic groups were
investigated. Owing to ionogenic groups a supramolecular network was
formed in the copolymer melts. We investigated the electric birefringence
in two copolymers P1 and P2 containing side-chain mesogenic groups COOCN
and ionogenic groups COOH. Sample P2 has ionic groups COO-Rb+
additionally. The Kerr constant K for samples P1 and P2 was found
comparable with that for gomopolymers with cyanobiphenyl side-chain
groups. The behavior of K fits correctly to the Landau-De Gennes
relation K~1/(T-T*). In contrast, the copolymers' dynamic
electrooptic properties dramatically differ from that of gomopolymers.
Times of dipole orientation (tdip)
and relaxation (t) of the induced
orientation order parameter in structured copolymers exceed those found in
gomopolymers more then 100 fold at temperatures near the isotropic-nematic
phase transition. The unusual temperature dependence of the relaxation
time t cannot be described in the
framework of the Landau–De Gennes theory.
COLL
195: Electro-optic study of model suspensions from cloudy apple
juice
Ivana B. Petkanchin1, Kiril Mihalev2, Maria
Buleva1, and Plamen Mollov2. (1) Institute of
Physical Chemistry, Bulgarian Academy of Sciences, Acad. G. Bontchev str.,
bl. 11, Sofia 1113, Bulgaria, petkanch@ipchp.ipc.bas.bg, (2) Higher
Institute of Food and Flavor Industry
Abstract
Electro-optics is applied to study the surface electric properties and
dimensions of the solid particles in suspensions obtained from cloudy
apple juices. The model suspensions from different types of apples are
prepared by a reproducible washing and separation procedure. The particles
are approximated as prolate ellipsoids with axial ratio about 1.5, as
indicated in the literature. The long axis of the particles varied between
5,000 nm and 4,800 nm in the pH range (3.5 – 5.5) studied. The electric
polarizability and the measured electrophoretic mobility increase with pH,
whereas the measured relaxation time of disorientation decreases. The
results correlate with the stability of real cloudy apple juices. The
results obtained show the importance of the additional charge
characteristic (electric polarizability) for the stability of such model
systems and allow to study the influence of some additives like pectin,
sugars, organic acids, etc.
COLL
196: Electrical properties of a fluorine-containing ionomer, PPFNA
Akira Minakata1, Motoko Kimura1, Shin-iti
Yano2, Yoshito Tanaka3, Takayuki Araki3,
and Tetsuo Shimizu3. (1) Department of Physics, Hamamatsu
University School of Medicine, 1-20-1 Handayama, Hamamatsu 431-3192,
Japan, Fax: +81-53-436-8691, aminak@nifty.com, (2) Department of
Chemistry, Gifu University, (3) Daikin Industries Ltd
Abstract
Electrical conductivity of a fluorine-containing ionomer, PPFNA
(Poly(9H,9H-perfluoro-2,5-dimethyl-3,6-dioxa-8-nonenoic acid)) was studied
with special attention to the effect of salt. This polymer is a
poly(carboxylic acid) but dissociates strongly. Neutralization with NaOH
results in a decrease of conductance but the slope changes as the
neutralization proceeds. Addition of salt alters the slope, which means
that the salt effect is not simply expressed in terms of additivity.
Details of the results will be presented in the session, together with
other studies on the solution properties.
COLL
197: Alignment control of monodispersed acrylic particles for
application in structural color materials
Tetsuya Yoshida, R&D center, Soken Chemical & Engineering,
1-13-1 Hirosehigashi, Sayamashi, Saitama 350-1320, Japan, Fax:
042-953-1859, rd-kiso@soken-ce.co.jp
Abstract
Structural color is the general term of the phenomenon of coloring due to
reflection, interference and scattering of light. It fundamentally differs
from the usual coloring by dyestuffs or pigments. Typical structural
colors are observed as the reflection of light from the three-dimensional
crystal lattice that is formed from fine particles of sub-micron size.
This study was performed to prepare this type of structural color. We
produced monodisperse acrylic particles by emulsion polymerization, and
particle size was controlled precisely. The particle size was 100-300 nm,
with very narrow distribution. The crystal alignment of these particles
was achieved by two methods. One is utilizing capillarity which occurs
when the emulsion dries, and the other is electrophoresis. Moreover, in
order to absorb the scattered light occurring inside the crystal, the
particles were dyed with some dyestuffs. By both methods, we succeeded to
obtain crystals with beautiful structural colors from blue to red.
COLL
198: Ion absorption on mangrove cell walls
Kenichiro Kimura, and Masafumi Yoshida, Chemistry Division,
Musashi Institute of Technology, 1-28-1, Tamazutsumi, Setagaya-ku, Tokyo
158-8557, Japan, Fax: +81-3-3323-7576, myoshida@po.iijnet.or.jp, myoshida@po.iijnet.or.jp
Abstract
In order to use mangroves in bio-remediation systems for polluted water,
experimental and computational studies were carried out for elucidating
the ion absorption mechanism of partially esterified pectins, the main
constituents of the mangrove cell wall. The measurements show that the
cation absorption rates linearly decrease with increasing esterification,
and that the selective ion absorption occurs around the esterified parts.
Such results are reproduced by molecular dynamics (MD) and Monte Carlo
Brownian dynamics (MCBD) simulations.
COLL
199: MgATP-induced conformational changes of myosin-extracted muscle
fibers measured by fluorescence microspectroscopy
Mieko Taniguchi1, Kouji Tani2, and Hiroomi
Aragane2. (1) Graduate School of Engineering, Nagoya
University, Furou-Chou, Chikusa-Ku, Nagoya, Japan, Fax: 052-789-3219,
mtanig@nubio.nagoya-u.ac.jp, (2) Division of Material Science, Graduate
School of Science, Nagoya University
Abstract
The role of MgATP on myosin-extracted muscle fibers (IZI-fibers) were
studied by time-resolved and static fluorescence microspectroscopy (using
synchrotron radiation at UVSOR). Spectral behavior depended on the
presence/absence of MgATP. Its effect on the fluorescence intensity was
found biphasic around p[MgATP]=5.5, suggesting a local conformational
change in the environment of tryptophan residues. With excitation at 295
nm and emission at 350 nm, the fluorescence intensity decay of IZI-fibers
showed the presence of three components (4.09, 2.02, and 0.21 ns) which
could be resolved by nonlinear least-squares analysis. We found from
static and dynamic fluorescence measurements that the role of MgATP on
myosin-extracted muscle fibers is to induce two conformers in the excited
states. We also found from atomic force microscopy that the occurrence of
conformational changes of myosin molecule depends on p[MgATP]. We will
discuss the interaction between myosin molecules and myosin-extracted
muscle fibers.
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