Multi-Scale Modeling Tools for the Membrane Formation Process Via Phase Inversion By Nonsolvent and Thermal Induced Phase Separation

Phase inversion, a process that occurs when a polymer collapses from solution into a thin film upon quenching or exposure to another phase, is the most widely used process for producing polymer membrane filters. The level of understanding of these manufacturing processes remains mostly empirical, with little theoretical basis to connect the process conditions and important quantitative membrane characteristics. This gap in knowledge necessitates a substantial amount of trial-and-error experimental work to discover and define the “process window” for a particular membrane product, which increases R&D costs and limits innovation of new membrane products or processes. We have developed two mesoscopic simulation models to examine the dynamics of the phase inversion process to predict the morphology of pore structures that develop within microporous polymer membrane filters. First, a coarse grained dissipative particle dynamics (DPD) method was used for modeling pore formation during nonsolvent induced phase separation (NIPS). This computational approach has incorporated millions of particles reaching nanometer length scales. Second, a novel phase field method was used for modeling pore formation during thermal induced phase separation (TIPS). This computational approach utilizes both Cahn Hilliard and Allen Cahn equations that are capable of predicting pore formation on the nano to micrometer length scales. The modeling tools developed will enable significant speed-up in membrane development. This talk will focus on initial results of the two methods and compare simulated structures and morphologies to current manufactured polymer membrane filters.