Unbiased evaluation of literature data on equilibrium melting temperature and enthalpy of fusion of perfectly syndiotactic polypropylene

The thermodynamic properties of highly syndiotactic polypropylene (PP) were reevaluated based on the data taken from the literature. The thermodynamic equilibrium melting temperature of a perfectly syndiotactic PP, which was estimated based on the Flory theory for the depression of the melting point in random copolymers, was 168.0°C. However, it was found to be 174.2°C when a linear extrapolation was attempted on a plot of the observed equilibrium melting temperature against the syndiotacticity level. The thermodynamic enthalpy of fusion of a perfect crystal of fully syndiotactic PP was estimated to be 8.7 kJ mol⁻¹, and the average value of the literature data was 7.8 kJ mol⁻¹. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1603–1609, 2001