(747c) A Multi-Fluid Model of Phase-Inversion Membrane Formation

Industrial processes for producing polymer-based materials operate away from equilibrium, making the final microstructure â?? and thus the properties of the material â?? dependent on process history. Describing such processes by traditional simulation methods has proven difficult because of the confluence of complex thermodynamics and non-trivial fluid mechanics. We have recently developed a â??multi-fluidâ? simulation framework for examining the dynamics of multiphase polymer solutions that combines a field-theoretic approach to thermodynamics with continuum fluid mechanics. In this framework, we use a ternary polymer solution model to investigate the phase inversion process for making polymer membranes. After characterizing the model and methods, we investigate a number of important phenomena that occur across several length and time scales including (i) mass-transfer between the polymer film and the non-solvent bath, (ii) phase separation between polymer lean and polymer rich regions and (iii) long-time coarsening behavior. We will further discuss the implications of these results on the formation mechanisms of various microstructures found in polymer membranes.