Statistical thermodynamics theory of phase equilibria in mixtures of thermotropic liquid crystals and flexible polymers

Lebwohl-Lasher model of nematogens and Flory-Huggins lattice model of polymers have been combined to describe the phase equilibria in mixtures of thermotropic small molecular liquid crystals and flexible polymers. The main aim is to calculate the phase diagram of the mixture in which the molecular weight of polymers is relatively high. It is found that the isotropic interaction between polymer segment and the liquid crystal is important and it results in the isotropic/isotropic demixing before isotropic/nematic demixing. The calculated results quantitatively agree with the experimental results quite well. Therefore, the results lend a support to the general validity of Lebwohl-Lasher model and Flory-Huggins model. Besides, the theory provides a theoretical method for designing the polymer dispersed liquid crystal electro-optical materials.

Sample Duplication Method for Monte Carlo Simulation of Large Reaction-Diffusion System

The sample duplication method for the Monte Carlo simulation of large reaction-diffusion system is proposed in this paper. It is proved that the sample duplication method will effectively raise the efficiency and statistical precision of the simulation without changing the kinetic behaviour of the reaction-diffusion system and the critical condition for the bifurcation of the steady-states. The method has been applied to the simulation of spatial and time dissipative structure of Brusselator under the Dirichlet boundary condition. The results presented in this paper definitely show that the sample duplication method provides a very efficient way to sol-’e the master equation of large reaction-diffusion system. For the case of two-dimensional system, it is found that the computation time is reduced at least by a factor of two orders of magnitude compared to the algorithm reported in literature.

Reaction-induced phase separation in rubber-modified epoxy resin

The phase separation mechanism,and structure development during curing of epoxy with a novel liquid rubber-ZR were investigated by time-resolved light scattering,optical microscope and differential scanning calonmetry (DSC) The mixture loaded with curing agent was a single-phase system in the early stage of curing.When the cure reaction proceeded,phase separation took place via the spinodal decomposition induced by polymerization of epoxy resin.This was supported by the characteristic change of light scattering profile with curing time.Cure reaction plays an important role in the progress of phase separation.The bigger the cure reaction rate is,the longer periodic distance will be.The overall two-phase structure was basically locked in when the conversion approached 80% estimated by DSC,and finally the co-continuous two-phase structure was successfully obtained.