Core-shell structured PVDF@BT nanoparticles for dielectric materials: A novel composite to prove the dependence of dielectric properties on ferroelectric shell

Abstract

The design of core-shell structure is considered as a facile approach to obtain polymer composites with excellent dielectric properties and high breakdown strength (Eb). In this work, thiol-terminated poly(vinylidene fluoride) (PVDF-SH) and polystyrene (PS-SH) are synthesized by a two-step process. The as-prepared polymers are applied to modify BaTiO3 (BT) nanoparticles. The subsequent morphologies, dielectric properties, and Eb of PVDF-based composites are investigated systematically. PVDF encapsulated BT (PVDF@BT) fillers carries more desirable compatibility with matrix compared with PS encapsulated BT (PS@BT) and raw BT. For instance, the Eb of the 30 vol% PVDF@BT composites slightly decreased from 150.6 to 117 kV/mm for PVDF matrix, as compared to the raw and PS@BT composites, for those the values intensively reduced to 58.5 kV/mm and 107 kV/mm, respectively. It is also observed that PVDF polymer shells play a significant role in the improvement of composites dielectric constant (εr). Moreover, the design of the polymer shell also contributes to the suppression of dielectric loss. The results are of great importance for understanding the effect of polymer shells and fluorinated filler on composite properties. This study provides a strategy for preparing composites with high εr while maintaining high Eb for the next generation of dielectric capacitors. Keywords: Dielectric nanocomposites, PVDF shell, Breakdown strength, Dielectric constant