GAS-TRANSPORT PROPERTIES OF HIGHLY FLUORINATED POLYAMIDEIMIDES

Gas transport properties of a series highly fluorinated polyamideimide s based on 2,2-bis(3,4-decarboxyphenyl)hexafluoropropane dianhydride a nd N, -phenyl)-perfluoroalkane-alpha,omega-dicarboxamide diamines have been measured as a function of upstream pressure and temperature. The results show that the permeability coefficients P for the penetrant g ases in any of the four polyamideimides decrease in the gas order: P(C O2) > P(O-2) > P(N-2) > P(CH4), while the permeabilities for a given g as in these polymers increase with the increase of oligo(tetrafluoroet hene) segment length. The effects of the substitution pattern of the p henyl ring and the length of the oligo(tetrafluoroethene) segments in the diamine moieties on gas permeabilities, diffusivities and solubili ties are discussed. It seems that, comparing with the effect of the fl exible oligo(tetrafluoroethene) segment, the substitution patterns of phenyl group in the diamine moieties have no notable effect of the dif fusivities in the polyamideimides as the length of the oligo(tetrafluo roethene) segment increasing from 8 to 12 carbons. The activation ener gies of permeation and diffusion were obtained for the gas/polymer pai rs studied and correlated with the size of penetrant gas. (C) 1997 Els evier Science Ltd.