(729c) Core-Shell Nanoparticles Filled Block Copolymer Nanocomposites for High Energy Density Dielectric Capacitors

The polymer nanocomposites offer unparalleled control over the composite properties by synergistic coupling of matrix and filler properties. In particular, polymer nanocomposites are highly advantageous for use as dielectric materials since they combine high dielectric breakdown strength of the polymer matrix and the high dielectric permittivity of the nanofillers, thus resulting in very high energy density, which is desired for the next-generation dielectric capacitors. However, the ceramic nanofillers which are needed for dielectric applications, suffer from poor dispersion, and hence sub-optimal properties, in the polymer matrix due to differences in the surface energies of the polymer and the filler. In this work, we use polymer grafted ceramic nanoparticles, which include poly(methyl methacrylate) grafted Barium Titanate (PMMA-g-BaTiO₃) and poly(methyl methacrylate)-block- polystyrene grafted Titanium Dioxide (PMMA-b-PS-g-TiO₂) as highly dispersible nanofillers in the polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) matrix for the formulation of high permittivity and high dielectric strength nanocomposites. The PMMA-g-BaTiO₃ nanoparticles were synthesized by surface-initiated atom transfer radical polymerization (ATRP) technique to have different grafting densities, different chain lengths by varying the feed ratios of ATRP initiator functionalized BaTiO₃ with methyl methacrylate (MMA), while the PMMA-b-PS-g-TiO₂ nanoparticles were synthesized by grafting to technique. The molecular weight of PMMA-g-BaTiO₃ nanoparticles ranged from 22 kg/mol to 100 kg/mol while that of PMMA-b-PS-g-TiO2 nanoparticle was found to be 27 kg/mol. The grafted nanoparticles showed good dispersion when mixed with homopolymer (PMMA) and block copolymer (PS-b-PMMA) matrices. In particular, the nanofillers segregate to the PMMA region of the block copolymer domains, which helps in achieving ordered nanostructures and thereby enhances the dielectric breakdown strength along with permittivity control. These novel nanocomposites offer unprecedented control over the dielectric properties of the nanocomposites and could be game-changer materials for next-generation dielectric capacitor applications.