FREE-VOLUME DISTRIBUTIONS OF POLYSTYRENE PROBED BY POSITRON-ANNIHILATION - COMPARISON WITH FREE-VOLUME THEORIES

Positron annihilation spectroscopy has been applied to measure the fre e-volume hole distributions in polystyrene (T(g) = 95-degrees-C, molar weight 105 000) as a function of temperature. The hole volume distrib utions are determined from orthopositronium distributions. The hole vo lumes are distributed between 35 and 200 angstrom3. The fractions of f ree volumes are distributed from 2.0 % to 11 % of total volume. The ob tained free-volume distributions are compared and discussed with the e xperimental distributions obtained by photochromic and florescent prob es and with the Turnbull-Cohen free-volume theory. The distributions o f free-volume fractions fit well with the theoretical function accordi ng to the Simha-Somcynsky lattice model.