Gelation mechanism of thermoreversible poly(vinylidene fluoride) gels in glyceryl tributyrate

Abstract

Poly(vinylidene fluoride) (PVF₂) gels in glyceryl tributyrate (GTB) with fibrillar morphology in the dried state. The gels are transparent and WAXS results indicate the presence of α-phase PVF₂ crystals in the gels. The gelation rate (t^-1_gel) has been measured by the test tube tilting method and has been analysed with the equation t^-1_gel ∝ f(c)f(T), where f(c) = concentration function and f(T) = temperature function. At a fixed temperature, the variation of t^-1_gel with concentration suggests that the nature of the connectedness in this system obeys the three dimensional percolation mechanism. On the other hand, at a fixed concentration, the variation of the gelation rate with temperature suggests that the gelation is a two step concerted process of conformational ordering and crystallization, the former acting as the rate determining step. The formation of fibrillar gels in this system has been attributed to the solvation of the TGTG conformer of PVF₂ through compound formation in a 3:1 molar ratio of the monomeric units of PVF₂ and GTB.