Core-shell structured barium titanate-poly(glycidyl methacrylate) (BaTiO3-PGMA) nanocomposites were prepared by surface-initiated atom transfer radical polymerization of GMA from the surface of BaTiO3 nanoparticles. Fourier transform infrared spectroscopy confirmed the grafting of the PGMA shell on the surface of the BaTiO3 nanoparticles cores. Transmission Electron Microscopy results revealed that BaTiO3 nanoparticles are covered by thin brushes (similar to 20 nm) of PGMA forming a core-shell structure and thermogravimetric analysis results showed that the grafted BaTiO3-PGMA nanoparticles consist of similar to 13.7% PGMA by weight. Upon incorporating these grafted nanoparticles into 20 lm-thick films, the resultant BaTiO3-PGMA nanocomposites have shown an improved dielectric constant (epsilon = 54), a high breakdown field strength (similar to 3 MV/cm) and high-energy storage density similar to 21.51 J/cm(3). AC conductivity measurements were in good agreement with Jonscher's universal power law and low leakage current behavior was observed before the electrical breakdown field of the films. Improved dielectric and electrical properties of core-shell structured BaTiO3-PGMA nanocomposite were attributed to good nanoparticle dispersion and enhanced interfacial polarization. Furthermore, only the surface grafted BaTiO3 yielded homogenous films that were mechanically stable. (C) 2014 Wiley Periodicals, Inc.