The program consists of a series of studies aimed at a basic understanding of the mechanisms controlling the formation of asymmetric membrane structures by the phase inversion method. An important aspect of the experimental program will be to develop optical techniques for measuring mass transfer rates and solvent-nonsolvent flux ratios during film quenching. Such data will be used in conjunction with a recently developed mass transfer model to both predict and correlate the nature of the phase separation processes during film precipitation. Experiments will be carried out on crystallizable and non-crystallizable membrane forming systems under a variety of quench bath conditions. A series of studies of the gelation mechanisms will also be carried out using DSC and falling-ball methods. These will be combined with analyses of the ternary (polymer, solvent, nonsolvent) phase diagram to evaluate the effects of possible transitions leading to gelation. Finally improvements and extensions of our model for the quench period will be undertaken to develop models of the simultaneous mass transfer-phase separation processes leading to the asymmetric structures. The basic understanding obtained in the program would provide building blocks for achieving improved, engineered membranes with superior, tailored separation properties.
