Gas permeation in polyarylates: effects of polarity and intersegmental mobility

Abstract

Permeability coefficients for He, Ar, O₂, N₂, CH₄, and CO₂ in five polyarylates synthesized from a mixture of iso: terephthalic acids (1:1) and a bridge substituted bisphenol were measured at a pressure of 1.0 × 10⁶ N/m² and temperature of 35°C. Bisphenols used for the syntheses of these polyarylates were prepared by substituting one of the bridge methyl groups (-CH₃) in bisphenol-A with one of the following functional groups: ethyl (-CH₂-CH₃), isobutyl (-CH₂-CH(CH₃)₂), phenyl (-C₆H₅), or methyl propionate (-CH₂-CH₂-COOCH₃). This type of substitution does not affect the polymer packing significantly. The calculated Hildebrand solubility parameter for these polyarylates also varies only in a narrow range. With these critical parameters being constant, the polyarylate permeabilities correlate well with increasing chain stiffness as indicated by secondary transition temperatures (T_τ°C). Substitutions which increased polarity had a negative effect on transport properties.