LOCALIZED RELAXATIONS IN THE GLASSY STATES OF SEVERAL MOLECULAR MATERIALS BEFORE AND AFTER THEIR POLYMERIZATION

Dipolar diffusion in the glassy and supercooled liquid states of 12 mo lecular substances and of their linear chain or network polymerized st ates formed by condensation polymerization at different temperatures a nd times have been studied by measuring the dielectric absorption for a fixed ac frequency of 1 kHz. The study showed that as the extent of polymerization increased with increasing isothermal temperature of pol ymerization, the sub-T-g relaxation peak due to localized molecular mo tions in the molecular state became gradually extinct, and a correspon ding peak at a higher temperature evolved and reached its maximum heig ht. The temperature of the sub-T-g relaxation peak in the polymerized state differed from that of the alpha-relaxation peak of the supercool ed molecular liquid by as much as 70 K, but, in several cases, the two temperatures were similar. Reasons for the latter occurrence are give n in phenomenological terms, It is concluded that the localized relaxa tion modes of the polar segments of the macromolecule are not related to the modes of molecular diffusion in the monomeric liquid state abov e its T-g. The localized relaxation characteristic of the glassy molec ular state persists in the incompletely polymerized state, where it is seen as a gamma-relaxation. (C) 1995 American Institute of Physics.