Effect of ionic liquid on crystallization kinetics and crystal form transition of poly(vinylidene fluoride) blends

Semicrystalline poly(vinylidene fluoride) (PVDF) incorporated with ionic liquids(IL) exhibits applicability as electrolyte. In this paper, crystallization kinetics and crystal form transition of PVDF blending with ionic liquid (1-hexyl-3-methylimidazolium chloride, [HMIM]Cl) were studied by using differential scanning calorimetry, Fourier transform infrared spectroscopy (FTIR), and X-ray scattering. Tg of the PVDF/[HMIM]Cl blends are higher than that of the pure PVDF, suggesting the strong interaction between [HMIM]Cl and molecular chains of PVDF. With the ionic liquid content increased, both the conductivities of solvent casting and reheated films increased with little difference between them when the [HMIM]Cl content is same. For normalization, we introduce relative time tr to replace t to eliminate the influence of cooling rate. Pure PVDF had the fastest crystallization rate through the crystallization kinetics. By addition of the [HMIM]Cl, the tr1/2 has a positive correlation, while the XtA has negative correlation with the degree of crystallization of the PVDF/[HMIM]Cl blends. What’s more, [HMIM]Cl promotes the formation of PVDF β phase during the recrystallization process, which is confirmed by FTIR and X-ray scattering. This study gives a clue for the development of high-quality gel polymer electrolytes.