Effect of Cation Type on the Isothermal Crystallization of Poly(vinylidene fluoride) Blended in Ionic Liquids with Eu(tta) 4 − Anion

To develop smart materials with tailored functional response, the combination of poly(vinylidene fluoride) (PVDF) and advanced ionic additives such as ionic liquids (ILs) is increasingly being investigated. Depending on the processing conditions, the incorporation of these additives into PVDF, together with their functional response, promotes the nucleation of specific electroactive phases. This work explores the effect of incorporating sodium tetra(2-thenoyltrifluoroacetonate) europate(III), NaEu(tta)4 and 1-butyl-3-methylimidazolium tetra(2-thenoyltrifluoroacetonate) europate(III), BmimEu(tta)4, into PVDF matrices through a comprehensive analysis of isothermal crystallization behavior, morphological features, crystalline phase development, and dielectric behavior. Field-emission scanning electron microscopy (FESEM) was used to analyze the microstructure, while Fourier transform infrared (FTIR) spectroscopy was used to assess the development of PVDF crystalline phases during its isothermal crystallization at various temperatures. All samples exhibited α, β, and γ crystalline phases, although their relative proportions differed significantly depending on the type of filler used. This suggests that BmimEu(tta)4 is a strong promoter of the electroactive (EA) phases of PVDF. The results are attributed to the interaction between the IL charges and the PVDF dipoles of the EA structures, which are promoted by higher crystallization temperatures, as supported by both FTIR and DSC data. Thus, the addition of NaEu(tta)4 and BmimEu(tta)4 strongly influences the crystallization kinetics of PVDF and allows nucleation of specific phases of PVDF. Additionally, dielectric spectroscopy revealed that the nature of the cation strongly influences conductivity behavior, as demonstrated by the dielectric results. Overall, the incorporation of NaEu(tta)4 and BmimEu(tta)4 not only influences the crystallization kinetics of PVDF but also provides PVDF with intrinsic functional properties such as luminescent behavior and improved electrical performance, offering a simple and efficient strategy of nucleating specific PVDF phases.