Structural Studies of Phase Transitions in Poly(di-n-alkylsiloxanes). 1. Poly(dimethylsiloxane) and Poly(diethylsiloxane)

Raman studies of poly(dimethylsiloxane) [PDMS] and poly(diethylsiloxane) [PDES] have been carried out from room temperature to -263 °C (10 K). Several bands characteristic of either the backbone or the allyl side chains have been identified and their bandwidth and frequency position followed as a function of temperature. A number of phase transitions, initially observed by DSC measurements, have been evaluated in terms of the molecular mobility introduced into the backbone and side chain at the transition temperature. In the case of PDES, the low-temperature transition (-60 °C) can be classified as an order-disorder transition leading to the formation of a “condis” crystal. © 1987, American Chemical Society. All rights reserved.