Fabrication of Barium Titanate Nanoparticles-Polymethylmethacrylate Composite Films and Their Dielectric Properties

A method for incorporating barium titanate (BT) nano-particles into polymethylmethacrylate (PMMA) is proposed to prepare composite films with a high dielectric constant and high transparency. BT particles with particle sizes of 7.8-24.0 nm and crystal sizes of 8.60-17.7 nm were synthesized with a complex alkoxide method. Surface of the BT particles was modified with 3-methacryloxypropyltrimethoxysilane to introduce double bonds that was grafted with PMMA. The PMMA-grafted BT particles were suspended in PMMA/N-methyl-2-pyrrodinone solution and spin-coated onto glass substrates to prepare the PMMA/BT composite films. The surface modification gave composite films having smooth surfaces and high transparency. An increase in BT particle size and BT volume fraction in the film tended to increase the dielectric constant while keeping the dissipation factor around 5%. The dielectric constant of the film prepared for a particle size of 24.0 nm at 39 vol% attained a value of 19.8 that was around four times higher than that of the pure PMMA film. The dielectric constants of the BT particles estimated by the application of Lichtenecker's mixing model to the composite films were 75.3, 105.1, and 166.3 for particle sizes of 7.8, 11.0, and 24.0 nm, respectively. POLYM. ENG. SCI., 49:1069-1075, 2009. (C) 2009 Society of Plastics Engineers