Abstract

Dielectric materials with high electric energy densities and low losses are of significant importance for a number of advanced engineering applications in modern electronic and electrical power systems. Compared with ceramics, fluoropolymers such as poly(vinylidene fluoride)(PVDF) and PVDF-based copolymer, namely poly-(vinylidene fluoride-co-hexafluoropropene) (P(VDF−HFP)), poly(vinylidene fluoride−trifluoroethylene) (P(VDF−TrFE)), poly(vinylidene fluoride-cochloride trifluoride ethylene) (P(VDF−CTFE)), and poly- (vinylidene fluoride−trifluoroethylene−chlorofluoroethylene) (P(VDF−TrFE−CFE)), have drawn more and more attentions of researchers worldwide due to their flexibility, easy molding and high breakdown strength along with high energy density. However, those PVDF-based polymers have relatively low dielectric constant and thus only low energy densities can be obtained at lower electrical field. In order to mitigate the above-mentioned problems, fillers especially conductors usually have been employed. Nevertheless, aggregation of nanomaterials has an adverse impact on interfacial polarization, which results in low breakdown strength. Two main strategies have been utilized to prepare well compatible dielectric polymer nanocomposites. The first one is directly encapsulating nanomaterials with active polymers like polydopamine (PDOPA) and polyvinyl pyrrolidone (PVP). In this case, organic shells prevent aggregation of nanomaterials in the polymer matrix, which decreases the leak current between the nanomaterials and accordingly improves the electrical properties of composites. In addition, organic ligands with hydroxyl, amidogen or fluorinated chains are introduced to attain well dispersion of nanomaterials in the polymer matrix. Moreover, the interaction of hydrogen bonding between the organic molecules and PVDF-based polymer can induce orientation of fluorine atoms which is beneficial to form more ferroelectric phrases