Positron investigations of free-volume elements in polymer gas-separation membranes

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