Investigations Of Preparations And Properties In Modification Of PVDF By Ionic Liquid

Poly(vinylidene fluoride)(PVDF)belongs to one of the most promising matrix for dielectric applications for their excellent properties such as good weather ability,high flexibility,and low dielectric loss.1-butyl-3-vinylimdazolium tetrafluoroborate([BVIM][BF4])was used as additive ionic liquid(IL)and a series of IL as well as its copolymers have been used to modify PVDF.The relative properties of the composites were characterized systematically.The main researches and conclusions are as follows:1.PVDF-IL blends were prepared by melt blending process.SEM results showed that no phase separation occurred obviously in all the samples,even in the sample with 10wt%IL,which indicated the good compatibility between PVDF and IL.Crystallization analysis proved the crystal transformation of PVDF from ?-phase to ?-phase,and the existence of the IL impeded the crystallization of PVDF.Moreover,the obtained blends exhibited excellent dielectricity and conductivity,and the elongation at break increased with the incorporation of IL.2.PVDF-PIL blends were prepared using two steps.Firstly,IL was homopolymerized in N,N-dimethylacetamide(DMAc)by the solution polymerization method to prepare PIL.Secondly,PVDF and PIL blends were prepared by melt blending process.The polymerized IL integrated in the form of macromolecular structure,which improved the stability of IL in the blends and inhibited the leakage in some applications.It was found that the obtained blends showed non-polar ? phase and decreased elongation at break.The increase of dielectric constant was not obvious.In addition,the incorporation of PIL played a role of nucleate agent,which had a good effect on crystallization of PVDF.3.PVDF/P(MMA-co-IL)composites were prepared by in-situ copolymerization.Methyl methacrylate(MMA)and IL monomers were in-situ copolymerized by the free radical copolymerization method in PVDF solution with N,N-dimethylacetamide(DMAc)as solvent.The MMA was used as co-monomer to improve the miscibility of the P(MMA-co-IL)and PVDF.The polymerized IL and MMA integrated in the form of macromolecular structure and the leakage issue of IL still could be resolved.Grafting analysis showed that more than 60% P(MMA-co-IL)were grafted onto the PVDF chains.SEM showed that no phase separation took place obviously for the most composites due to the incorporation of MMA.FTIR and XRD measurements indicated the crystaltransformation of PVDF from ?-phase to ?/? phase,and the incorporation of P(MMA-co-IL)inhabited the crystallization ability of PVDF matrix.Moreover,the PVDF/P(MMA-co-IL)composites showed higher dielectric constant and electrical conductivity,and the the elongation at break increased significantly.