Molecular motions near the glass transition in diethylene glycol bis(allyl carbonate) as studied by dielectric relaxation spectroscopy

Abstract

The monomer diethylene glycol bis(allyl carbonate), used commercially to produce CR39 resin for optical lenses and safety apparatus, has been studied by dielectric relaxation spectroscopy in order to characterise fully the component dipolar relaxations. Various theoretical functions have been used to fit the dielectric relaxation spectra obtained above the glass transition temperature. The principal relaxation (α-process) which is associated with the main glass transition of the monomer arises from the co-operative motions of dipoles. It was found to behave in a non-Arrhenius manner, and indicates that at –95 °C and below the monomer behaves as a glass, at higher temperatures up to –60 °C it is a viscoelastic solid, and at temperatures above –60 °C the sample is a supercooled liquid. The origins of the dielectric α-relaxation process are discussed in terms of recent approaches including mode-mode coupling theory, models of dynamic heterogeneity and MD computer simulations.