GAS PERMEATION PROPERTIES OF PHENYLENE OXIDE POLYMERS

Gas permeability (P-i) and diffusion (D-i) coefficients in respect to several gases (H-2, O-2, N-2, CO, CO2, CH4) have been measured for pol y(2,6-dimethylphenylene oxide) (PMPO), poly(2,6-diphenylphenylene oxid e) (PPPO), and phenylene oxide copolymers containing methyl, phenyl, a nd allyl radicals as side groups. X-ray diffraction study shows that b oth homopolymers are semicrystalline materials, whereas all the copoly mers are completely amorphous. The results show that a replacement of methyl by phenyl groups in PMPO/PPPO pair is accompanied by a decrease in the P values. A transition from semicrystalline PMPO to amorphous copolymers results in a decrease in permeability and solubility coeffi cients and not in a growth of these parameters as can be expected on t he basis of the behavior of other semicrystalline polymers (e.g. polyo lefins). It is supposed that the crystallites of PMPO, and possibly of PPPO are packed loosely and, hence, take part in sorption and gas tra nsport. This assumption is in agreement with numerous X-ray data as we ll as the results of positron annihilation study of these polymers. (C ) 1998 Elsevier Science B.V.