The influence of head-to-head defects on the crystallization of PVF2

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Abstract
The high temperature crystallization behavior of poly(vinylidene fluoride) is studied by differential scanning calorimetry as a function of the concentration of reversed monomer units, or head-to-head (H/H) defects. As has been reported, α and γ forms may exist in the crystallized samples, depending on the crystallization temperature. The equilibrium melting temperature of the α form is obtained from the Hoffman-Weeks plot. It is found to decrease linearly with the H/H defect content. The observed melting temperature is linear with the logarithm of the crystallization time, in accord with the nucleation theory of homopolymers. Lamellar thickening, as measured by the rate of increase of the melting temperature, is apparently independent of the crystallization temperature and the H/H defect content. The crystallinity decreases with both the H/H defect content and the molecular weight.