Abstract
Conformational changes are observed during sub- T g annealing of solution-cast films of BPA–polycarbonate by following changes in the conformationally sensitive IR aromatic breathing band at 1600 cm −1. The rate of conformational relaxation is compared with published data on enthalpy and volume relaxation on the same polymer. The relaxation rates and timescales converge in the immediate vicinity of T g, but diverge at temperatures below T g−15 K and conformational energy only accounts for a very small fraction of observed enthalpy relaxation. The results suggest that a single process is active in volume and conformational relaxation and that at least two processes contribute to enthalpy relaxation.
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