| Flory's equation of state analysis was performed for several PP/diluent systems undergoing thermally-induced phase separation (TIPS). Model systems were chosen to represent several phase separation behaviors. Interaction parameters and phase diagrams were estimated and confirmed by comparison with experimental data from melting temperature depression and cloud point measurements. A simple, reliable methodology to provide the equation of state parameters developed. The free volume effect was significant due to the dissimilarity of equation of state properties between polymer and diluent. The enthalpic interaction increased with increasing diluent end group polarity. Increased diluent chain length decreased the free volume effect within each class of diluent. The interaction parameters for the PP/n-alkane systems were nearly constant with temperature resulting in the system stability. The interaction parameters for the PP/n-fatty acid systems decreased slightly with increasing temperature resulting in an unstable region at temperatures below the PP crystallization curve. The interaction parameter for the PP/TA system greatly increased with decreasing temperature resulting in upper critical solution temperature behavior. Consequently, PP/n-alkane systems underwent solid-liquid phase separation, PP/n-fatty acid systems underwent solid-liquid phase separation when slowly cooled and liquid-liquid separation when quenched, and PP/n,n-bis (2-hydroxyethyl) tallowamine (TA) system underwent liquid-liquid phase separation or solid-liquid phase separation, depending on the initial composition.; The influence of thermodynamic and kinetic parameters on TIPS membrane structure was investigated. The parameters studied were thermodynamic interaction parameter, diluent size, composition, cooling condition, and the diluent crystallization temperature. The role of each parameter was determined by examining membrane structures using scanning electron microscopy, and interpreting the results in terms of the initial solution thermodynamics and the membrane propagation procedure. The membranes formed via TIPS usually have a dual structure with inter- and intra-spherulitic pores. The coarsening of phase separated domains after spinodal decomposition was experimentally confirmed.; Membrane structure can be varied through proper selection of polymer and diluent and appropriate manipulation of the cooling conditions. The procedures detailed in Chapters 2 and 3 facilitate the polymer and diluent selection, and the studies outlined in Chapter 4 serve as a guideline for controlling the cooling conditions. |
