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 (BaTiO3) and poly(methyl methacrylate) (PMMA) matrix is reported to expand the application field for composite films such as displays and touch panel screens. BaTiO3 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 BaTiO3 nanoparticles were then added to a sample of methyl methacrylate to obtain a transparent BaTiO3 dispersion. Transparent BaTiO3/PMMA nanocomposite films (sheet type, thickness of 150 μm) are obtained by the polymerization of the BaTiO3/MMA dispersion via heat treatment and by using a polymerization initiator. The visual transparency of the BaTiO3/PMMA film is comparable to that of the original PMMA film. Additionally, no difference in the transparency of the BaTiO3/PMMA films is observed when the BaTiO3 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 BaTiO3. 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