Effects of the addition of protic organic solvents and the sample formation processes on the crystal structure of poly(vinylidene fluoride): Detailed mechanism of promoting the formation of the β-phase

Abstract

Poly(vinylidene fluoride) (PVDF) is a well-known piezoelectric polymer. To promote the formation of the β-phase crystal, which accounts for the piezoelectricity of PVDF, this study examined the effect of adding a protic organic solvent (p-OS) to a spinning solution of PVDF for electrospinning (ES) and investigated the influence of the sample formation process by comparing with film samples prepared by the bar-coating and spin-coating methods. Methanol (MeOH), ethanol (EtOH), and acetic acid (AAc) were utilized as the p-OSs. Regarding the ES samples, the crystallinity, χc, of PVDF was unaffected by the additions of the p-OSs, while a fraction of the electroactive β- and γ-phase crystals, FEA, exhibited a maximum against the amount of p-OS. To clarify the mechanism of the effect of p-OSs on electroactive phase formation, Fourier-transform infrared (FT–IR) spectra of the samples were obtained in the solution or gel states, which assumed the conditions during the ES process.