The temperature dependence of positron annihilation characteristics,3 andI3, has been studied on sample of poly(butadiene), poly(isobutylene) and poly(chloroprene). The temperature range was between 15 and 470 K. The rate of expansion of holes or free-volume in all samples was deduced belowTg as well aboveTg as appr. 3·10–3 K–1 and 2·10–2 K–1, respectively. These values are very close to the rate of the mean squared displacement of scatterer<r2>observed in neutron scattering experiments. A possibility to use an inverse value of free-volume,Vf–1
for study of viscoelastic state of polymers is demonstrated.