Epoxy‐based hybrids using TiO₂ nanoparticles prepared via a non‐hydrolytic sol–gel route

Abstract

TiO 2 nanoparticles with an average diameter of less than 10 nm were prepared via a non-hydrolytic sol-gel route in a TiCl 4 -diisopropyl ether-CH 2 Cl 2 system. After modification with n-octylphosphonic acid (OPA) to increase their organophilic character, the TiO 2 nanoparticles were used for preparation of TiO 2 /epoxy hybrid films. Characterization by FT-IR, solid-state 13 C cross-polarization/magic angle spinning (CP/MAS) and 31 P MAS NMR techniques showed the preservation of the n-octyl groups and the presence of Ti-O-P bonds on the surface of TiO 2 nanoparticles. Hybrid films with various TiO 2 contents were prepared via a wet process and casting using CH 2 Cl 2 as a solvent. The resulting films were highly transparent. The refractive indices of TiO 2 /epoxy hybrid films at 633 nm increased monotonously from 1.51 for the pure polymer to 1.66 for the hybrid containing 62.4 mass% of TiO 2 nanoparticles.

Preparation of Transparent Bulk TiO2/PMMA Hybrids with Improved Refractive Indices via an in Situ Polymerization Process Using TiO2 Nanoparticles Bearing PMMA Chains Grown by Surface-Initiated Atom Transfer Radical Polymerization

“…Although polymers have been widely used as optical materials because of their transparency, light weight, excellent formability, and low cost, their applications in optical materials requiring high refractive indices have been limited because common optical polymers such as poly­(methyl methacrylate) (PMMA) and epoxy resin have a restricted range of refractive indices of from 1.3 to 1.7 . Organic–inorganic hybrids bearing inorganic nanoparticles with high refractive indices (TiO 2 nanoparticles (refractive indices of 2.5–2.7), for example) have therefore attracted attention for their ability to overcome the limitations on the refractive indices of common polymers. − Although optical polymers with refractive indices enhanced by molecular design have been recently developed, demand remains for improvement of optical properties using commercially available polymers by incorporating nanoparticles for various industrial applications, including optical waveguides, lenses, antireflective coatings, , and LED encapsulations. , …”

Synthesis and Characterization of Anatase TiO2 Nanorods: Insights from Nanorods’ Formation and Self-Assembly

“…In these reactions, the oxygen for the oxide NPs formation is provided by the solvent (ethers, alcohols, ketones, or aldehydes) or by the organic constituent of the precursor (alkoxides or acetylacetonates) [30,36]. Along with that, several key condensation reactions are proposed depending on the precursor and solvent in the reaction system such as alkyl halide elimination by a titanium alkoxide and a titanium halide reaction [27,29,35], ester elimination between titanium carboxylates and titanium alkoxides reaction [30,34], and ether elimination by two titanium alkoxides reaction [37].…”

Modification of TiO2 Nanoparticles with Oleyl Phosphate via Phase Transfer in the Toluene–Water System and Application of Modified Nanoparticles to Cyclo-Olefin-Polymer-Based Organic–Inorganic Hybrid Films Exhibiting High Refractive Indices

“…Compounds such as carboxylic acids, silane coupling reagents, and phosphorus coupling reagents ,− are commonly employed to modify the surfaces of TiO 2 nanoparticles. Phosphorus coupling reagents are attractive for binding organic groups because the Ti–O–P bonds formed are highly stable with respect to hydrolysis, and homocondensation between the phosphorus coupling reagents is unlikely to occur under moderate conditions .…”