Optical and scanning electron microscope observations of substrate effects on the crystallization of polyvinylidene fluoride from solution

Abstract

In has been more than a decade since it was first reported that drawn polyvinylidene fluoride (PVDF) film showed large piezo- and pyro-electric effects. This polymer has been the subject of intense investigation, partly because of its commercial application to transducers and infra red (IR) sensors. PVDF can exist in at least five distinct polymorphs, three of which are electrically active [1], There are reasons to believe that polymorphism is more the rule than the exception in macromolecules. Recently, we showed that crystallization of PVDF from solution onto different substrates gave rise to different polymorphs [2]. The structure of cast PVDF varied between α, β and γ forms, or mixtures of them, depending on the nature of the substrate. X-ray diffraction scans of PVDF cast on glass or silicon showed a peak located at 2θ ≃ 20.5°, which we attributed to a possible precursor of the β form.