Transparent and high permittivity films were prepared by melt pressing poly(methyl methacrylate) (PMMA)-grafted 7 nm barium titanate (BT) particles. PMMA chains with molecular weights of 32-40 kDa were grafted on BT particle surfaces at a density of 0.2-0.7 chains nm(-1) through surface initiated atom transfer radical polymerization of methyl methacrylate. This yielded BT/PMMA composites with BT volume fractions (4) ranging from 3.2% to 10%. In melt-pressed BT/PMMA composite films, BT particles were well-dispersed and exhibited high transmittance at 550 nm, with the values standardized for 100 mm thickness being 80%. The relative permittivity of the films at 1 kHz and 25 degrees C increased to 4.1 upon increasing 4 to 10%, according to Lichtenecker's logarithmic mixture formula, while the loss tangent remained as low as 0.04. (C) 2015 Elsevier Ltd. All rights reserved.