This research will focus upon porous polymeric materials exhibiting a uniform sub-micron cell size which show great promise in applications such as membranes, catalyst supports, artificial skin, etc. Current liquid-based phase separation technologies for producing these materials are limited be difficulties in solvent removal and structural heterogeneity introduced by thermal gradients. It is proposed to generate uniform, cellular polymeric materials via a micro-phase separation induced in a polymer network swollen by a supericrtical fluid. By taking advantage of the strong dependence of solvent power on pressure, a unique characteristic of supercritical fluids, one can assume finer control over the microstructure in porous materials than is presently available using conventional liquid solvents. The research program will be divided into two phases. In the first, the equilibrium swelling composition and the relaxation behavior of a polymer network exposed to supercritical CO2 will be measured using a quartz spring microbalance and dielectric spectrometer, respectively. These will be the first such measurements on a network/supercritical fluid system. In the second phase, microporous materials will be generated via a phase separation in a supercritical fluid- swollen network. Porosity will be measured using conventional techniques and correlated with the fundamental thermodynamic information compiled during the initial program phase.
