Preparation of Core-shell Structured Polystyrene/BaTiO3 Nanoparticles via in situ RAFT Polymerization for High-performance Dielectric Nanocomposites

The incorporation of high-dielectric-constant ceramic nano-filler into polymer matrix is an important approach to prepare polymer composites with excellent dielectric performance. However, the easy aggregation of inorganic nano-filler generally not only results in poor film quality and inhomogeneities, but also affects the dielectric performance. Herein, a novel route to prepare core-shell structured nanocomposites with excellent dielectric performance is reported. The promising approach using in situ RAFT polymerization to graft polystyrene (PS) from the BaTiO3 surface, and the insulating polymer shells not only act as interlayers to prevent the agglomeration of the nanoparticles, but also act as the matrix. The PS shell thickness could be well controlled by adjusting the feed ratio of styrene to BaTiO3. The dielectric performance of the PS@BaTiO3 nanocomposites is studied by broadband dielectric spectroscopy from 1 Hz to 1 MHz at room temperature. The dielectric constant of the nanocomposites is significantly enhanced (more than 7.9 times) as the BaTiO3 content increasing and the dielectric loss is maintained in a relatively low level (< 0.015). Moreover, the dielectric constant of such nanocomposites has weak frequency dependence in a very wide frequency range.