Phase separation kinetics in reactive and non-reactive multi-component polymer systems.

摘要

Much of the work in modeling and computer simulation of spinodal decomposition has been done for binary systems. This dissertation investigates the phase separation kinetics of a multi-component polymer system, with or without reaction of which the non-reactive system accounts for the majority. This work attempts to carry out the analysis of spinodal decomposition in ternary polymer/solvent/non-solvent systems, where the solvent is the monomer used to produce the polymer and the non-solvent is the major component. Phase separation occurred when the temperature was raised above the LCST (Lower Critical Solution Temperature) of the system. A generalized diffusion equation was derived in order to analyze the spinodal decomposition for a multi-component system. Various experimental methods were used to determine values for model parameters, such as cloud point experiments, time-resolved light scattering in the ternary system, and morphological development of polymer membranes formed during the early stages of spinodal decomposition. Through a combination of experimental methods and computer simulation work, we can determine the approximate parameters needed to model the early stages of spinodal decomposition in a ternary polymer/solvent/non-solvent system. These parameters were determined for a ternary version of the Cahn-Hilliard expression of spinodal decomposition and the resulting set of partial differential equations was solved numerically. Diffusion coefficients were obtained for both the three parameter and five parameter models describing a ternary system.; A reactive system model was obtained by adding a free-radical polymerization reaction term to the spinodal decomposition diffusion equation. Numerical simulation data shows that larger interdomain distances were obtained at higher reaction rates.