GAS-TRANSPORT PROPERTIES OF SOLUBLE POLY(PHENYLENE SULFONE IMIDE)S

Gas transport of helium, hydrogen, carbon dioxide, oxygen, argon, nitr ogen, and methane in three soluble poly(phenylene sulfone imide)s base d on 2,2-bis(3,4-decarboxyphenyl) hexafluoropropane dianhydride (6FDA) has been investigated. The effects of increasing length of well-defin ed oligo(phenylene sulfone) units on the gas permeabilities and diffus ivities were determined anti correlated with chain packing of the poly mers. Activation energies of diffusion and permeation were calculated from temperature-dependent time-lag measurements. The influences of th e central group in the diamine moiety of 6FDA-based polyimides on phys ical and gas transport properties are discussed. The incorporation of a long oligo(phenylene sulfone) segment in the polymer backbone decrea ses gas permeability and permselectivity simultaneously. The decreases in permeability coefficients can be mainly related to decreases in di ffusion coefficients. Changing the central group of diamine moiety fro m -S- to -SO2- leads to a 45-50% decrease in CO2 and O-2 permeabilitie s without appreciable increase in the selectivities. This is considere d to be due to the formation of charge transfer complexes. (C) 1997 Jo hn Wiley & Sons, Inc.