MICROHETEROGENEITY OF POLYMERS NEAR THE GLASS-TRANSITION TEMPERATURE

A number of linear and network polymers were studied in the temperature range of glass transition (T-g - 100 K, T-g+ 100 K) with the ESR spin probe method and NMR. It was found that there is a certain temperature interval (T-g, T-g + Delta T; Delta T = 30 - 70 K), where polymers studied manifest spatial inhomogeneity. Domains characterized with different segmental mobility and having spatial dimensions about 100 Angstrom and lifetime over 1 ms were discovered in network polyurethanes. The mechanism of spin diffusion together with the mechanism of polarization transfer related to the Rouse-type mobility of macromolecules were taken into account in order to estimate the spatial dimensions of inhomogeneities on the basis of experiments on spin polarization transfer.