Relaxation behaviour in bulk PIMA and PIMA-PMMA copolymer near Tg
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 ϕμ(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 ϕμ(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.
Key wordsPIMA PMMA PCS dielectric spectroscopy relaxation
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