POSITRON-ANNIHILATION IN POLYVINYLALCOHOL DOPED WITH CUCL2

Positron annihilation lifetime spectra were measured for polyvinylalco hol doped with CuCl2 (0.5 to 5.0wt%) at temperatures rising from 30 de grees C to 160 degrees C (heating run) and then from 160 degrees C dow n to room temperature (cooling run). The data clearly revealed the gla ss transition (T-g) at around 90 degrees C. Both I-3 and tau 3 were de creased by the added CuCl2, being interpreted as the result of inhibit ion and quenching. Both the inhibition coefficient alpha and the quenc hing rate constant kappa were smaller than the corresponding values in liquids. The diffusion constant of ortho-positronium (o-Ps) estimated from kappa implies that o-Ps is not very mobile in the polymer. For a ll the samples tau(3) below T-g was always larger in the heating runs than in the cooling runs, but above T-g tau(3) was the same for heatin g and cooling runs. This is due to the existence of strain brought abo ut by the process of preparation of the samples. Copyright (C) 1996 El sevier Science Ltd.