Confined Ferroelectric Properties in Poly(Vinylidene Fluoride‐co‐Chlorotrifluoroethylene)‐graft‐Polystyrene Graft Copolymers for Electric Energy Storage Applications

Abstract

Dielectric polymer film capacitors having high energy density, low loss and fast discharge speed are highly desirable for compact and reliable electrical power systems. In this work, we study the confined ferroelectric properties in a series of poly(vinylidene fluoride‐co‐chlorotrifluoroethylene)‐graft‐polystyrene [P(VDF‐CTFE)‐g‐PS] graft copolymers, and their potential application as high energy density and low loss capacitor films. Thin films (ca. 20 μm) are prepared by different processing methods, namely, hot‐pressing or solution‐casting followed by mechanical stretching at elevated temperatures. After crystallization‐induced microphase separation, PS side chains are segregated to the periphery of PVDF crystals, forming a confining interfacial layer. Due to the low polarizability of this confining PS‐rich layer at the amorphous–crystalline interface, the compensation polarization is substantially decreased resulting in a novel confined ferroelectric behavior in these graft copolymers. Both dielectric and ferroelectric losses are significantly reduced at the expense of a moderate decrease in discharged energy density. Our study indicates that the best performance is achieved for a P(VDF‐CTFE)‐g‐PS graft copolymer with 34 wt‐% PS; a relatively high discharged energy density of approximately 10 J cm−3 at 600 MV m−1, a low dielectric loss (tanδ = 0.006 at 1 kHz), and a low hysteresis loop loss (17.6%) at 550 MV m−1.

Rational Design and Modification of High-k Bis(double-stranded) Block Copolymer for High Electrical Energy Storage Capability

“…The conductive I 2 -doped PA and ions (nanoscale HCD) were wrapped in the core of a hollow nanosphere, and their η values were relatively high, which were 85.6 and 85.7% with the I 2 content of 2.5 and 5 mol % (Table S5), respectively. Finally, compared with some previous all-polymeric dielectrics, ,,,,− the energy densities versus efficiencies of the nanoscale HCD-contained copolymer PBNPF 30 - b - PBHPF 30 -( b - PTNP 200 ) 2 films without or with 2.5 and 5 mol % I 2 showed a combination of high energy density and efficiency level (Figure ), which seem to be better candidates for dielectric materials in comparison to the reported most polymer dielectrics.…”

Novel Ferroelectric Polymers for High Energy Density and Low Loss Dielectrics

“…A natural extension of the above work is to further increase the PS content in the PVDF copolymer. In a recent study, we grafted different length PS side chains (1.9–7.6 repeat units in each side chain) from P­(VDF–CTFE) 93/7 using ATRP followed by dechlorination. , When the PS graft content is 17 wt %, a similar antiferroelectric-like behavior as that for the P­(VDF–TrFE–CTFE)- g -PS­(14%) in Figure B is seen. When the PS graft content is above 30 wt %, linear hysteresis loops are observed for the P­(VDF–CTFE)- g -PS graft copolymers.…”

Facile grafting modification of main-chain-type semi-fluorinated alternating fluoropolymers via simultaneous CuAAC reaction and ATRP in one pot at ambient temperature

“…As the integration ratio of the alternating copolymer (A 2 B 1 ) n A 2 between peaks b, c, and d was nearly 2 : 1 : 2, demonstrating the correctness of the alternating structure and no loss of iodine atoms on the copolymer backbone. In the 19 F NMR spectrum of (A 2 B 1 ) n A 2 (Fig. 1b), the chemical shifts a′ and b′ also show the existence of the end group -CF 2 CF 2 H and its chain-end functionality is close to 100%.…”

“…The structure of the graft copolymer (A 2 B 1 ) n A 2 -g-PPEGMA was also confirmed by 1 H NMR and 19 F NMR spectra (Fig. S14 †), indicating that the "one-pot" process was successful.…”