Formation and saturation of β-phase of PVDF in DMF solvent: a comprehensive study

In the present work, we report the effect of solvent content on the β-phase fraction in PVDF (poly(vinylidene fluoride)) films synthesized by the facile wet chemical route using DMF (N,N-Dimethylformamide) as the solvent. The amount of PVDF powder was kept fixed while the amount of DMF was varied. X-ray diffraction (XRD) revealed the transformation of the α-phase in the PVDF powder to β-phase in the synthesized PVDF films which was further confirmed by Fourier Transform Infrared Spectroscopy (FTIR) and Differential Scanning Calorimetry (DSC) measurements. Deconvolution of the XRD profiles of the films showed the increase of the β-phase content (viz. β/α ratio) with initial increase of the DMF volume. However, a surprising and previously unreported result emerged, i.e. the saturation of the β-phase beyond a certain volume of the solvent. The plausible mechanism for the formation and saturation of the β-phase in the PVDF films is discussed.