GAS-TRANSPORT PROPERTIES OF POLYARYLATES - SUBSTITUENT SIZE AND SYMMETRY EFFECTS

Gas transport of helium, hydrogen, oxygen, nitrogen, methane, and carbon dioxide gases in a series of polyarylates based on isophthalic acid has been examined. These polyarylates were prepared from dimethyl-Bisphenol A, tetramethyl-Bisphenol A, diisopropyl-Bisphenol A, and dibromodimethyl-Bisphenol A monomers to study the effects of varying Bisphenol substituent group size, symmetry, and polarity. Symmetrical placement of substituent groups increases permeability while asymmetrical placement lowers permeability. Substitution of a tertiary butyl group at position 5 on the isophthalate ring increases polymer permeability. Most of the increases in permeability can be related to increases in the diffusion coefficients of all the gases. The isophthalate of dibromodimethyl-Bisphenol A has gas separation properties very similar to those of the tetrabrominated analog.