Positronium as a probe of sorption mechanism in polytetrafluoroethylene

Abstract

As one of the series of works of application of positron annihilation technique to the study of sorption of polymers, sorption of CO 2 and CH 4 into polytetrafluoroethylene has been measured. The lifetimes of the two o-Ps states, τ 3=1.6 ns and τ 4=4 ns in vacuum, were increased with the charged gas pressure. The intensity of the longer lived component, I 4, was decreased showing that the sorbed molecules and o-Ps are competing for the free volume sites in the amorphous parts. The intensity of the shorter lived component, I 3, did not decrease substantially. From these results it is concluded that the τ 3 component corresponds to o-Ps annihilating in the interphase region between the crystalline and amorphous parts. It has also been deduced from the results that positronium increases the size of the holes.