POSITRON INVESTIGATIONS OF FREE-VOLUME ELEMENTS IN POLYMER GAS-SEPARATION MEMBRANES

This work is a part of an investigation aimed at converting the positr on method into a tool for quantitative investigations of microdefects in polymers. The number (10(19) cm(-3)) and effective radii (0.2-2.8 n m) of elementary free volumes in polymer gas-separation membranes poly trimethyl silylpropine (PTMSP) and porous polyphenylene oxide (PPO 200 and 70 m(2)/g) are estimated on the basis of positron data. The calcu lations are facilitated by using the mutually complementary programs P ATFIT and CONTIN as well as by the possibility of estimating the diffu sion coefficients of positronium in PPO samples having different speci fic surface areas. (C) 1998 American Institute of Physics.