Abstract
The properties of the free volume hole in pure and doped poly(vinyl chloride) (PVC) have been investigated as a function of cadmium content and temperature using positron annihilation lifetime and Doppler broadening of annihilation radiation techniques. The observed spectra were decomposed into three components, with the longest component (lifetime, τ 3 and intensity, I 3) being associated with the pick-off annihilation of o-Ps trapped by free volume. The temperature coefficient of τ 3 and I 3 showed a change at the glass transition temperature ( T g) to lower temperature. Further, the behavior of the annihilation parameters was different during the heating and cooling cycles. These observations are correlated with observations of the electrical conductivity. The free volume hole and the fractional free volume were also derived from the positron annihilation parameters. A correlation between the fractional free volume and conductivity above T g was experimentally confirmed using measured positron annihilation results. The value of the critical volume for doped PVC is found to be larger than that for pure PVC. This larger difference might be the result of the existence of large ionic charge carriers.
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