(243a) Predicting Morphology For Membranes Formed Via Liquid – Liquid Tips

A deterministic approach was taken to predict membrane morphologies resulting from the matrix solidification step that occurs in the formation of microporous membranes via liquid ? liquid thermally induced phase separation (L?L TIPS). Many studies have examined the growth rate of droplets in the coarsening stage of membrane formation, but few have attempted to extend this information into the subsequent processing steps of matrix solidification, diluent extraction/exchange, and drying. In the research presented here, the approach taken to model matrix solidification utilized Monte-Carlo routines to provide quantitative information on cell size and cell size distribution for a representative polymer ? diluent system. The model accounted for shrinkage due to crystallization of the polymer-rich phase, diluent expulsion from the polymer-rich phase, and continued droplet growth during the solidification process, but did not seek to include blooming effects in which diluent is expelled to the surfaces of the membrane. The predicted structures were compared to experimentally formed membranes. The effect of extraction on membrane morphology was shown experimentally to be negligible and therefore was not included in the modeling. The drying stage was simulated using finite element analysis to investigate the effects of capillary pressures in deforming the final membrane structure.