Enhanced Breakdown Strength of Ferroelectric Polymer Films for Capacitive Energy Storage by Incorporating Oriented Fluorographene

Ever-increasing electrification scenarios call for high energy density (Ue) polymer nanodielectric films beyond the commercial benchmark biaxially oriented polypropylene. Ferroelectric polymers of intrinsic high dielectric constant εr, if integrated with improved breakdown strength (Eb) and dielectric loss from nanofillers, would be a promising paradigm for high-Ue polymer nanodielectrics. Yet, this expectation is still in its infancy because of the great challenge of increasing the Eb and needs introduction of new approaches. Here, fluorographene (FG), as a young halogen derivative of graphene, is employed as an emerging nanofiller to develop high-Eb polymer nanodielectrics. A dramatically enhanced Eb, which is 39.4% higher than that of a neat polymer film from casting, is achieved in a composite film along with a reduced dielectric loss by incorporating only 0.2 wt % FG with in-plane orientation from electrospinning. The origin of such a high Eb-reinforcing effect of FG is traced by both experimental characterizations and phase-field simulation. It is found that the in-plane oriented FG of appropriate loading level would induce both the favorable low crystallinity of the polymer matrix and the FG–polymer interface with deep traps and less defects. This, together with the high out-of-plane insulation of FG from a high fluorine/carbon ratio, regulates the charge behaviors and breakdown paths and thus significantly enhances the voltage endurance of composite films. The results demonstrate the remarkable Eb-reinforcing effect of emerging FG fillers in polymer nanodielectrics and offer a strategy toward high-Eb/high-Ue flexible dielectric capacitors

UV-Catalytic Preparation of Polypyrrole Nanoparticles Induced by H₂O₂

As a green oxidant, H₂O₂ can be used to induce the polymerization of pyrrole. This approach avoids the issue of metal residue in the polymer caused by metal oxidants, whereas the reaction efficiency is low and the corresponding reaction mechanism not clear. In this study, uniform polypyrrole (PPy) nanoparticles were prepared using H₂O₂ as an oxidant under UV irradiation in the presence of polyvinylpyrrolidone (PVP). The morphology characterization indicated that the spherical PPy nanoparticles were capped by a PVP shell. Through the investigation of reaction process, it was found that the photolysis of H₂O₂ led to the formation of hydroxyl radicals, which then initiated the oxidative polymerization of pyrrole. The coalescence of small PPy particles formed nanoparticles which were stabilized by PVP. The effects of several reaction conditions on the polymerization rate and the size distribution of nanoparticles were investigated in detail, including radiation intensity (0–30 W), temperature (0–50 °C), and the concentrations of PVP (5–20 g/L), H₂O₂ (0.06–0.6 M), H₂SO₄ (0–0.<i>2</i>2 M), and the monomer pyrrole (0.03–0.2 M), respectively. UV-catalytic preparation of PPy nanoparticles induced by H₂O₂ is an effective and environmentally friendly approach, which could be expected to be extended to other conductive polymers