POSITRON-ANNIHILATION IN POLYVINYLALCOHOL DOPED WITH CUCL2

Positron annihilation lifetime spectra were measured for polyvinylalco hol (PVA) doped with CuCl2 (0.5 to 5.0 wt%) at temperature range from room temperature to 160 degrees C. For a fresh pure PVA (without annea ling) tau(3) below T-g was larger in the heating runs than in the cool ing runs, but above T-g, tau(3) was the same for both runs. The larger tau(3) values in the heating run were considered to be due to the exi stence of strain brought forth in the process of preparation. For anne aled pure PVA tau(3) was the same for the heating and the cooling runs add T-g was shifted to lower temperature, 88 and 80 degrees C for fre sh and annealed samples, respectively. Thin shift was attributed to lo ss of H-bonded water in the annealed pure PVA by heating above 100 deg rees C. Both I-3(0) and tau(3) were decreased by the added CuCl2, bein g interpreted as the result of inhibition and quenching, respectively. The results show that both the inhibition coefficient alpha and the q uenching rate constant k were smaller than the corresponding values in liquids, The small diffusion constant of o-Ps estimated from k implie s that o-Ps is not very mobile in the polymer.