The formation of the γ phase from the α and β polymorphs of polyvinylidene fluoride

Thermal, optical, infrared, and x-ray techniques are used to demonstrate that the γ phase of polyvinylidene fluoride can be obtained from existing α- and/or β-phase crystallites by either an annealing-induced solid state α→γ phase transformation or as the result of a slow melting and recrystallization process. It is shown that certain surfactants modify the melting behavior of the α and β phases in a manner that accelerates the rapid recrystallization of the γ form. PVF2 samples that contain only the γ polymorph can be produced by this surfactant-controlled technique. It is postulated that the surfactant delays the diffusion of molecules freed in the melting process and thus increases the probability of the stabilization of conformational fluctuations that result in the γ phase.