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Articles 151 - 159 of 159

Full-Text Articles in Polymer Science

Phase Equilibria Of A Nematic And Smectic-A Mixture, Hao-Wen Chiu, Thein Kyu Feb 1998

Phase Equilibria Of A Nematic And Smectic-A Mixture, Hao-Wen Chiu, Thein Kyu

College of Polymer Science and Polymer Engineering

A phase diagram of a mixture consisting of nematic and smectic liquid crystals has been calculated self-consistently by combining Flory-Huggins (FH) theory for isotropic mixing and Maier-Saupe-McMillan (MSM) theory for smectic-A ordering. However, the MSM theory can be deduced to the original Maier-Saupe (MS) theory for nematic ordering. To describe the phase transitions involving induced smectic phase and nematic + smectic equilibrium, two nematic and two smectic order parameters for the nematic/smectic mixtures have been coupled through the normalized partition function and the orientation distribution function. Self-consistent numerical solution has been sought in establishing nematic/smectic phase diagrams involving (i) phase …


Phase Diagrams Of A Binary Smectic-A Mixture, Hao-Wen Chiu, Thein Kyu Nov 1997

Phase Diagrams Of A Binary Smectic-A Mixture, Hao-Wen Chiu, Thein Kyu

College of Polymer Science and Polymer Engineering

A variety of smectic phase diagrams involving smectic-isotropic and smectic-nematic-isotropic transitions have been calculated based on a combination of Flory-Huggins (FH) theory for isotropic mixing and Maier-Saupe-McMillan (MSM) theory for smectic-A ordering of liquid crystals (LC). To describe the mesophase transitions, two nematic order parameters and two smectic order parameters have been coupled through the normalized orientation distribution and partition functions. Flory-Huggins interaction parameter (chi) for isotropic mixing and the coupling term involving the nematic interaction parameter (nu) and the McMillan smectic interaction parameter (alpha) for phase transitions of liquid crystals have been incorporated in the calculation. The predictive capability …


Nucleation Initiated Spinodal Decomposition In A Polymerizing System, Thein Kyu, Jae Hyung Lee May 1996

Nucleation Initiated Spinodal Decomposition In A Polymerizing System, Thein Kyu, Jae Hyung Lee

College of Polymer Science and Polymer Engineering

Dynamics of phase separation in a polymerizing system, consisting of carboxyl terminated polybutadiene acrylonitrile/epoxy/methylene dianiline, was investigated by means of time-resolved light scattering. The initial length scale was found to decrease for some early periods of the reaction which has been explained in the context of nucleation initiated spinodal decomposition We have combined the Cahn-Hilliard kinetic equation and polymerization kinetics, and predicted the initial reduction of the length scale triggered by nucleation.


Non-Markovian Brownian Motion In A Viscoelastic Fluid, V. S. Volkov, Arkadii I. Leonov Apr 1996

Non-Markovian Brownian Motion In A Viscoelastic Fluid, V. S. Volkov, Arkadii I. Leonov

College of Polymer Science and Polymer Engineering

A theory of non-Markovian translational Brownian motion in a Maxwell fluid is developed. A universal kinetic equation for the joint probability distribution of position, velocity, and acceleration of a Brownian particle is derived directly from the extended dynamic equations for the system. Unlike the extended Fokker-Planck equation which corresponds to Mori-Kubo generalized Langevin equation and provides only with calculations of one-time moments, the universal kinetic equation obtained gives complete statistical description of the process. In particular, an exact generalized Fokker-Planck equation in the velocity space valid for any time instant is derived for the free non-Markovian Brownian motion. It shows …


Equilibrium Phase-Behavior Of Nematic Mixtures, Hao-Wen Chiu, Thein Kyu Nov 1995

Equilibrium Phase-Behavior Of Nematic Mixtures, Hao-Wen Chiu, Thein Kyu

College of Polymer Science and Polymer Engineering

A phenomenological model for predicting phase diagrams of a binary nematic mixture containing side chain liquid crystalline polymers and/or low molar mass liquid crystals has been proposed by combining Flory-Huggins free energy of isotropic mixing and Maier-Saupe free energy for nematic ordering of the nematogens. Two orientational order parameters, s(1) and S-2, Of the two components in the mixtures having two different clearing temperatures are taken into consideration in the calculation. The Flory-Huggins interaction parameter, chi, and the nematic interaction parameter of the Maier-Saupe theory, nu(1) and nu(22), are assumed to be functions of inverse absolute temperature. Further the cross-nematic …


Spinodals In A Polymer-Dispersed Liquid-Crystal, Chungsea Shen, Thein Kyu Jan 1995

Spinodals In A Polymer-Dispersed Liquid-Crystal, Chungsea Shen, Thein Kyu

College of Polymer Science and Polymer Engineering

Thermodynamic phase equilibria of a polymer dispersed liquid crystal (PDLC) consisting of
monomeric liquid crystals and a polymer have been investigated theoretically and experimentally.
The equilibrium limits of phase separation as well as phase transition of a PDLC system were
calculated by taking into consideration the Flory–Huggins (FH) theory for the free energy of mixing
of isotropic phases in conjunction with the Maier–Saupe ~MS! theory for phase transition of a
nematic liquid crystal. The correspondence between the Landau–de Gennes expansion and the
Maier–Saupe theory was found and the coefficients were evaluated. The calculation based on the
combined FH-MS theory predicted …


Polymerization-Induced Phase-Separation In A Liquid-Crystal-Polymer Mixture, J. Y, Kim, C. H. Cho, P. Palffy-Muhoray, M. Mustafa, Thein Kyu Oct 1993

Polymerization-Induced Phase-Separation In A Liquid-Crystal-Polymer Mixture, J. Y, Kim, C. H. Cho, P. Palffy-Muhoray, M. Mustafa, Thein Kyu

College of Polymer Science and Polymer Engineering

We have used light scattering to study the kinetics of polymerization-induced phase separation in a liquid-crystal-polymer mixture. The evolution of the structure factor is compared with scaling predictions for thermally quenched systems. We have also observed a cascading phenomenon where phase separated domains become unstable and undergo phase separation for a second time.


Phase-Separation Dynamics Of Polycarbonate Polymethyl Methacrylate Blends. I. Temperature Jumps Into An Immiscibility Loop, Dong-Soo Lim, Thein Kyu Mar 1990

Phase-Separation Dynamics Of Polycarbonate Polymethyl Methacrylate Blends. I. Temperature Jumps Into An Immiscibility Loop, Dong-Soo Lim, Thein Kyu

College of Polymer Science and Polymer Engineering

No abstract provided.


Phase-Separation Dynamics Of Polycarbonate Polymethyl Methacrylate Blends. Ii. Temperature Jumps Above An Immiscibility Loop, Thein Kyu, Ds Lim Mar 1990

Phase-Separation Dynamics Of Polycarbonate Polymethyl Methacrylate Blends. Ii. Temperature Jumps Above An Immiscibility Loop, Thein Kyu, Ds Lim

College of Polymer Science and Polymer Engineering

No abstract provided.