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.

Robust nanogenerators based on graft copolymers via control of dielectrics for remarkable output power enhancement

“…In a careful inspection of the 1 H nuclear magnetic resonance (NMR) spectra of the samples (Fig. 1B), the composition of the graft copolymers was calculated on a mole basis from the integral ratio of two noticeable resonances at 2.3 to 2.5 and 2.9 to 3.2 parts per million (ppm) attributed to head-to-head and head-to-tail configurations of PVDF and the signals at 1.4 to 1.65 ppm associated with the tert -butyl group in PtBA using the following equations ( 29 )$\mathrm{italicx}=\frac{false(\mathrm{italici}\mathrm{italicn}\mathrm{italict}\mathrm{italice}\mathrm{italicg}\mathrm{italicr}\mathrm{italica}{\mathit{l}}_{1.4-1.65}false)/9}{false(\mathrm{italici}\mathrm{italicn}\mathrm{italict}\mathrm{italice}\mathrm{italicg}\mathrm{italicr}\mathrm{italica}{\mathit{l}}_{2.3-2.5}+\mathrm{italici}\mathrm{italicn}\mathrm{italict}\mathrm{italice}\mathrm{italicg}\mathrm{italicr}\mathrm{italica}{\mathit{l}}_{2.9-3.2}false)/2}$$\text{PtBA mole percent} false(\text{mol}\%false)=\frac{\mathit{x}}{1+\mathrm{italicx}}\times 100$…”

Grafting PMMA onto P(VDF‐TrFE) by CF Activation via a Cu(0) Mediated Controlled Radical Polymerization Process

“…However, the energy loss is still high about 40–60% in these TrFE containing copolymers owing to the relaxation character of polar ferroelectric domains. By grafting low polar polystyrene (PS) onto the side chains of P(VDF‐CTFE) or P(VDF‐TrFE‐CTFE), the resultant graft copolymers exhibit the antiferroelectric‐like behavior with dramatically decreased energy loss, which may be attributed to the reduced coupling interactions among the ferroelectric domains. While, the poor compatibility and the weak intermolecular force between PS and PVDF chains result in the disappearance of the antiferroelectric‐like character under electric field over 300 MV m −1 and the decrease in U e .…”

Ferroelectric Polymers and Their Energy‐Related Applications

“…Recently, PVDF-based graft polymers with antiferroelectric-like behavior were synthesized by grafting low polarizable polymer side chains, i.e., polystyrene (PS) to the PVDFbased copolymer or terpolymer. [ 59,60 ] The synthesis is based on the atom transfer radical polymerization (ATRP) of styrene from the Cl sites of CTFE defects in PVDF-based copolymers or terpolymers. The double hysteresis loops observed in these graft polymers are quite stable even with high fi eld poling.…”