THE LOW-TEMPERATURE RELAXATION MECHANISMS IN POLY(VINYL ACETATE) - A THERMALLY STIMULATED CURRENTS STUDY

The dipolar relaxation behaviour of poly(vinyl acetate) has been studied extensively in the low temperature region from -160 to -20-degrees-C. It is shown that the observed relaxation peak does not correspond to a single relaxation process but to a continuous distribution of relaxation times. The components of this distribution show Arrhenius behaviour and the corresponding activation energies are low (approximately 8 kcal mol-1). which suggests that the dipolar motions involved are local motions, probably internal rotations about single bonds in the acetate groups. A continuous increase of the Gibbs activation energy for higher temperature components is observed, which is a consequence of a lowering of the activation entropy (the higher temperature relaxation modes have more negative activation entropies).