All-organic polymer dielectrics prepared via optimization of sequential structure of polystyrene-based copolymers

It is a great challenge to improve simultaneously the permittivity (εr) and breakdown strength of polymer dielectrics. The linear polystyrene (PS) has the advantages of low cost, easy processing and high charge-discharge efficiency (η). However, the low εr and low breakdown strength result in the low discharge energy density (Ue) of PS. For polar liquid crystalline polymer poly[11-((4′-cyano-[1,1′-biphenyl]-4-yl)oxy)undecyl methacrylate] (PCBMA), it shows the merit of high εr, low band gap width and good film-forming property. In this paper, random copolymers P(St-co-CBMA) and block copolymers PS-b-PCBMA were synthesized by radical polymerization and reversible addition-breaking chain transfer polymerization, respectively. The effect of sequential structure on the dielectric behaviors and energy storage properties of polystyrene copolymers is investigated in detail. The experimental results indicate that a high εr value of 5.2 (±0.049), an outstanding Ue of 8.94 J/cm3 and high η of 87.4% at 476 MV/m are achieved in random copolymer P(St-co-CBMA) with the 92 mol% content of CBMA unit because of the strong orientation polarization, deep traps and good film-forming property. This work demonstrates that it is a feasible strategy to obtain high performance polystyrene copolymer dielectrics via tailoring sequential structure between functional monomer and styrene monomer.