Relaxation behaviour in bulk PIMA and PIMA-PMMA copolymer near T _g

Abstract

The relaxation processes in the glass-transition temperature range of bulk PIMA and PIMA-PMMA copolymer have been studied by means of Photon Correlation Spectroscopy (PCS) and dielectric spectroscopy (DR). The experimental results were treated in a conistent way employing an inverse Laplace transform analysis of the density C _ϱ(t) and dipole moment ϕ_μ(t) autocorrelation functions. The latter was obtained from the ɛ″ (ω) data utilizing a recently developed algorithm. For bulk PIMA, C _ϱ(t) clearly shows two distinct relaxation processes, whereas ϕ_μ(t) is dominated by the slower (α-) relaxation mode. The fast process in C _ϱ(t) is probably related to the rotation of the rigid isobornyl group about the C-O bond.

The copolymer displays a β-relaxation process and a slower α-relaxation dielectric process in agreement with the PCS results. The molecular origin of these processes is outlined.