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

Positron annihilation spectroscopy has been applied to measure the free-volume hole distributions in polystyrene (T(g) = 95-degrees-C, molar weight 105 000) as a function of temperature. The hole volume distributions are determined from orthopositronium distributions. The hole volumes are distributed between 35 and 200 angstrom3. The fractions of free volumes are distributed from 2.0 % to 11 % of total volume. The obtained free-volume distributions are compared and discussed with the experimental distributions obtained by photochromic and florescent probes and with the Turnbull-Cohen free-volume theory. The distributions of free-volume fractions fit well with the theoretical function according to the Simha-Somcynsky lattice model.