MOLECULAR MOTIONS NEAR THE GLASS-TRANSITION IN DIETHYLENE GLYCOL BIS(ALLYL CARBONATE) AS STUDIED BY DIELECTRIC-RELAXATION SPECTROSCOPY

The monomer diethylene glycol bis(allyl carbonate), used commercially to produce CR39 resin for optical lenses and safety apparatus, has bee n studied by dielectric relaxation spectroscopy in order to characteri se fully the component dipolar relaxations. Various theoretical functi ons have been used to fit the dielectric relaxation spectra obtained a bove the glass transition temperature. The principal relaxation (alpha -process) which is associated with the main glass transition of the mo nomer arises from the co-operative motions of dipoles. It was found to behave in a non-Arrhenius manner, and indicates that at -95 degrees C and below the monomer behaves as a glass, at higher temperatures up t o -60 degrees C it is a viscoelastic solid,and at temperatures above - 60 degrees C the sample is a supercooled liquid. The origins of the di electric alpha-relaxation process are discussed in terms of recent app roaches including mode-mode coupling theory, models of dynamic heterog eneity and MD computer simulations.