Transparent BaTiO₃/PMMA Nanocomposite Films for Display Technologies: Facile Surface Modification Approach for BaTiO₃ Nanoparticles

Fabrication of a transparent film composed of a barium titanate (BaTiO 3 ) and poly(methyl methacrylate) (PMMA) matrix is reported to expand the application field for composite films such as displays and touch panel screens. BaTiO 3 nanoparticles are synthesized by sol–gel route with dispersion carried out in 2-methoxyethanol. The synthesized nanoparticles are 10 nm in size and are highly dispersed in the solvent. The surfaces of the obtained nanoparticles are modified by treatment with titanium isopropoxide and by using two silane coupling agents: n -decyltrimethoxysilane and 3-(triethoxysilyl)propyl methacrylate. The surface-modified BaTiO 3 nanoparticles were then added to a sample of methyl methacrylate to obtain a transparent BaTiO 3 dispersion. Transparent BaTiO 3 /PMMA nanocomposite films (sheet type, thickness of 150 μm) are obtained by the polymerization of the BaTiO 3 /MMA dispersion via heat treatment and by using a polymerization initiator. The visual transparency of the BaTiO 3 /PMMA film is comparable to that of the original PMMA film. Additionally, no difference in the transparency of the BaTiO 3 /PMMA films is observed when the BaTiO 3 weight ratio is varied between 5% and 33%. The dielectric constant of the nanocomposite film improved from 4.6 (PMMA only) to 7.1 by incorporating 10 wt % of BaTiO 3 . Such improvement in the dielectric properties, while maintaining the transparency, flexibility, and workability of PMMA films, allows the expansion of the fields of functional ceramics and polymers.