Spectroscopic evidence and mechanistic insights on dehydrofluorination of PVDF in alkaline medium

Abstract

This study presents newer insights on the dehydrofluorination of poly(vinylidene fluoride), PVDF, in alcoholic sodium hydroxide using infrared (IR), Raman and nuclear magnetic resonance (1H and 1H {19F}) spectroscopies. Details on the reactivity of phases and site selectivity of different orientations viz head-to-tail and tail-to-tail is comprehensively examined using IR/Raman and NMR (1D and 2D), respectively. The α-phase is prominently involved in dehydrofluorination and transforms into the more electroactive β-phase. 1H NMR spectra highlight that the tail-to-tail addition of PVDF is not disturbed and remains unaffected during dehydrofluorination reaction. Furthermore, 1H-19F heteronuclear correlation spectroscopy (Hetero COSY) clearly evidences the formation of the –(CH=CF)– double bond in dehydrofluorinated PVDF. Moreover, detailed mechanistic insights of dehydrofluorination reaction and possible internal crosslinking during the chemical transformation is presented.