Achieving Superior Energy Storage Properties of All-Organic Dielectric Polystyrene-Based Composites by Blending Rod–Coil Block Copolymers

Abstract

With the excessive consumption of natural resources and the miniaturization trends of advanced electronic products and equipment, there is an urgent need to improve the energy density and efficiency of polymeric dielectrics. In this paper, we explore the effect of rod–coil block copolymer polystyrene-b-poly[bis(4-cyanophenyl) 2-vinylterephthalate] (denoted as PS-b-PBCN) on the dielectric behavior and energy storage properties of PS-based blend films. The dipolar glass rigid polymer PBCN can have a columnar nematic phase, a high glass-transition temperature of 156 °C, a high relative permittivity (εr) of 14, and a low band gap of ≈3.44 eV; however, it has poor film-forming properties. Linear dielectric PS possesses low cost, and good film-forming and insulation properties, with a low εr value of 2.5. Two types of PS-b-PBCN block copolymers (PS158-b-PBCN78 and PS158-b-PBCN16), including a coil PS block and an electronically polarized rod PBCN block, are fabricated via reversible addition–fragmentation chain transfer polymerization polymerization. The PBCN/PS- and PS-b-PBCN/PS-blended films are synthesized by solution casting. The experimental results indicate that the εr and breakdown strength of the blend films improve with an increasing mass content of homopolymer PBCN or block copolymer PS-b-PBCN. A maximum εr value of 5.8 at 1 kHz is obtained in the 30 wt % PS158-b-PBCN78/PS blend film owing to the good compatibility and high loading of the polar polymer PBCN. Moreover, a low dielectric loss of 0.018 is found. A discharged energy density of 2.16 J/cm3 with a high efficiency of 90% at 295 MV/m is achieved because PBCN can immobilize free electrons and restrict the long-distance migration of charges. This work provides an idea for the fabrication of all-organic PS-based dielectrics with a high energy storage performance by introducing rod–coil block copolymers.