Abstract
Heat capacity has been measured between 308 and 523 K for a number of polymers: four narrow-distribution polystyrene fractions and a non-fractionated polystyrene sample; statistical copolymers of styrene with methyl methacrylate and styrene with acrylonitrile; polycarbonate and polysulphone. The samples were first cooled from the melt at different rates. Parameters in the Moynihan model of enthalpy relaxation accompanying the glass transition were determined for the studied polymers. Empirical correlations were established between a phenomenological parameter characterizing the width of spectrum of relaxation times and the polymer molecular weight and, on the other hand, the dimensionless ratio ΔE/ RT g .
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