Preparation of high-refractive-index PMMA/TiO2 nanocomposites by one-step in situ solvothermal method

High-refractive index polymeric materials, which are transparent, have many promising applications in optical design and advanced optoelectronic fabrication. In order to improve the refractive index of polymeric materials, inorganic materials with high-refractive index, such as TiO2, are always added into polymers. However, some of the traditional synthetic methods are complicated and hard to control. In our work, we developed a novel and simple method, a one-step in situ solvothermal method, to prepare poly(methyl methacrylate) (PMMA) and nano-TiO2 hybrid films. Methyl methacrylate (MMA), vinyltrimethoxysilane (VTMO), titanium butoxide [Ti(OBu)4], ethanol, hydrochloric acid, azobis-isobutyronitrile and tetrahydrofuran were added into a reaction vessel altogether and the polymerization of PMMA matrix and the formation of nano-TiO2 composite carried out simultaneously. To improve the adhesion between PMMA and TiO2, VTMO was used as a comonomer. The results indicate that TiO2 nanoparticles produced by decomposition of titanium butoxide are dispersed homogeneously in the PMMA matrix. The size of TiO2 crystals in PMMA/TiO2 nanocomposites is about 5–6 nm. The hybrid films have a good transparency (over 80 %) in the visible region, a good thermal stability and a UV-shielding property after the incorporation of TiO2. The refractive index of as-formed PMMA/TiO2 nanocomposites increases up to 1.839 at 633 nm as the content of Ti(OBu)4 is 50.00 wt%.