Relaxations and phase transitions phenomena in structurally related tyrosine-derived polyarylates

Abstract

A series of four tyrosine-derived polyarylates with different number of methylene groups in the backbone (y = 2, 4, 6 and 8) were studied by measuring thermally stimulated depolarization currents (TSDC). The low temperature TSDC spectra (80—240K) were analyzed at two different degrees of hydration to assess the effects of small amounts of water in the observed broad and complex β band. Higher temperature TSDC spectra (250 to 350 K) provided the α relaxation peaks associated with the glass transition temperature. The direct signal analysis (DSA) method allowed the decomposition of the complex peaks into elementary processes. The βi components result from localized motions of molecular segments of variable length molecules whose identities were established in a prior study of polycarbonates. The changes observed in the low and high temperature polarization with the number of backbone methylene groups were interpreted as a combination of flexibility and entanglement phenomena.