No abstract

Dielectric polymer film capacitor is rapidly emerging as next-generation energy storage for advanced engineering applications because of its lightweight, low cost, and processability. Further increasing energy density of polymer film with high charge-discharge efficiency is prevalent research spotlight. The filler/polymer composite with compatible interface is proved as an effective strategy to improve the energy storage capability of dielectric film. In this work, we designed hyperbranched hexafluorobutyl acrylate copolymer as miscible interface in graphene/fluoropolymer dielectric composite. A facile one-pot method was adopted to synthesize hyperbranched polyethylene grafted hexafluorobutyl acrylate (HBPE-g-HFBA) copolymer, which was adsorbed on surface of nanosheets by non-covalent interaction during exfoliation of natural graphite. The graphene/poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) (P(VDF-TrFE-CFE)) composite was prepared by solution casting. The interfacial polarization is enhanced with the improved compatibility of composite that is due to the chemical similarity between hexafluorobutyl acrylate segments and fluoropolymer matrix. The energy density of 0.1 wt% nanocomposite achieves 5.0 J/cm3 with charge-discharge efficiency of 78.1% at 250 MV/m. This work provides an optional route for non-covalent functionalization of graphene and the development of flexible polymer film capacitor with large energy storage capability.

We herein demonstrate a universal strategy for producing fluorescent polymers (FPs) from conventional resins by adding designer hyperbranched polyethylene (HBPE) copolymers based on the aggregationenhanced excimer emission effect. As an example, a copolymer, HBPE@Py@ PGMA, that possesses an HBPE backbone simultaneously bearing pyrene terminal groups and poly(glycidyl methacrylate) (PGMA) side chains has been synthesized by combining Pd-diimine-catalyzed chain walking ethylene copolymerization and atomic transfer radical polymerization techniques, and epoxy resin-based composites have been obtained by physically mixing with the copolymer. It is found that while the PGMA side chains make the copolymer well dispersible in the epoxy resin matrix, the HBPE backbone can effectively promote the formation of intra/intermolecular pyrene excimers, thus rendering epoxy resin that can emit homogeneous and strong fluorescence even at extremely low pyrene concentrations (0.05−0.20 wt %). Representatively, other FPs also have been successfully prepared from the ethylene-vinyl acetate copolymer, poly(methyl methacrylate), and polystyrene by following this strategy.

Polymer film capacitor exhibits extensive applications in advanced electronics because of its flexibility and huge power density. The current research interests of polymer capacitor are addressed on large energy density and high chargedischarge efficiency of composite film. Here we developed the compatible elastic interface composed of hyperbranched poly(methyl acrylate) copolymer in graphene/poly(vinylidenefluoride-trifluoroethylene-chlorofluoroethylene) (P(VDF-TrFE-CFE)) nanocomposite with high energy capability. This hyperbranched copolymer comprising polyethylene core that was grafted with poly(methyl acrylate) (PMA) segments and pyrene units was synthesized by atom transfer radical polymerization. The few-layer graphene was exfoliated with assistance of hyperbranched copolymer that was attached on surface of flakes via π-π noncovalent interactions between pyrene groups and delocalized π electrons of nanosheets. Graphene/P(VDF-TrFE-CFE) nanocomposite film was prepared by solution casting method. The compatibility between graphene and fluoropolymer is greatly improved due to the elastic interphase of PMA segments in hyperbranched copolymer, which enhances the interfacial polarization and decreases the accumulation of charge carriers under high electric field. The energy density of 7.0 J/cm 3 with charge-discharge efficiency of 60% at 300 MV/m is achieved for 0.1 wt% nanocomposite. This work reveals an effective architecture of polymer composite with elastic interface to increase the energy capability of polymer dielectric film.