Effect of annealing on the phase transition in poly (vinylidene fluoride) films prepared using polar solvent

Abstract

The γ -phase poly (vinylidene fluoride) (PVDF) films are usually prepared using dimethyl sulfoxide (DMSO) solvent, regardless of preparation temperature. Here we report the crystallization of both α and γ -phase PVDF films by varying preparation temperature using DMSO solvent. The γ -phase PVDF films were annealed at 70, 90, 110, 130 and 160°C for five hours. The changes in the phase contents in the PVDF at different annealing conditions have been described. When thin films were annealed at 90°C for 5 h, maximum percentage of β -phase appears in PVDF thin films. The γ -phase PVDF films completely converted to α -phase when they were annealed at 160°C for 5 h. From X-ray diffraction (XRD), Fourier transform infrared spectrum (FTIR), differential scanning calorimetry (DSC) and Raman studies, it is confirmed that the PVDF thin films, cast from solution and annealed at 90°C for 5 h, have maximum percentage of β -phase. The β -phase PVDF shows a remnant polarization of 4.9 µC/cm² at 1400 kV/cm at 1 Hz.