(184b) Cavity Size, Sorption and Transport Characteristics of Thermally Rearranged (TR) Polymers

Within a polymer film, free-volume elements have a wide range of sizes and topologies. This broad range of free-volume element sizes compromises a polymer's ability to perform molecular separations. Herein, six permeable thermally rearranged (TR) polymers and their precursors were studied. Using atomistic models, cavity size (free volume) distributions determined by a combination of molecular dynamic and Monte Carlo methods are consistent with the observation that TR polymers are more permeable than their precursors. The cavity size distributions determined by simulation are also consistent with free volume distributions determined by positron annihilation lifetime spectroscopy. The diffusion, solubility and permeation of gases in TR polymers and their precursors were also simulated at 308 K. The simulation results qualitatively agree with experimental data.