A Polystyrene-4-vinylpyridine Copolymer with High Dielectric and Energy Storage Properties

Nonlinear dielectric polymers for high-power density capacitors generally possess a high dielectric constant (εr), a large breakdown electric field (Eb), but a large dielectric loss (tan δ) due to the relaxation of high polar dipoles. To address the inherent trade-off between dielectric response and loss, we propose a low polarity polystyrene-4-vinylpyridine (P(S-r-4VP)) multipolymer by incorporating a 4-vinylpyridine (4VP) into polystyrene (PS) using conventional emulsion polymerization. Interestingly, compared to pure PS, the π-electron density of P(S-r-4VP) is significantly improved for the addition of functional 4VP unit, thereby promoting the strong electronic polarization response under an electrical field. As such, εr and Eb of the P(S-r-4VP) films increase with molar content of 4VP, and reach to 3.7 at 100 Hz and ∼550 MV/m, respectively. Notably, the P(S-r-4VP) copolymer exhibits a considerable discharged energy density (Ue) of 3.43 J/cm3 under an electrical field of 500 MV/m. Thus, this work offers valuable insights for the application of polystyrene-based polymers in dielectric energy storage areas.