The influence of chain structure on the equilibrium melting temperature of poly(vinylidene fluoride)

Three poly(vinylidene fluoride) whole polymers were fractionated according to their head-to-head concentrations. Their melting temperatures and fusion properties were studied. Although small but significant differences were found among the fractions obtained from a given parent polymer, a wide range in chain compositions was not obtained. The equilibrium melting temperatures were determined by extrapolating the dependence of the observed melting temperature on the crystallization temperature. A critical analysis is given of this extrapolation method as applied to poly(vinylidene fluoride) and the results are compared with literature reports. The problems involved in explaining the dependence of the equilibrium melting temperatures on the structural irregularities of the chain are given. Possible reasons for the relatively high level of crystallinity that is observed, for what is essentially a copolymer, are also discussed