High refractive index transparent nanocomposites prepared by in situ polymerization

Abstract

High refractive index transparent nanocomposites have been developed by in situ polymerization of a precursor that contains functional monomers and surface modified anatase TiO₂ nanoparticles for optoelectronic applications. The monomers are in the liquid form, so environmentally friendly solventless precursors can be prepared. The precursor can be processed into various shapes or thick films (>50 microns) of the nanocomposite. The relationships of the chemical structure of the organic matrix, nanoparticle content and dispersity with the refractive index, transparency, mechanical and thermal properties are systematically investigated. The refractive index, and mechanical and thermal properties of the nanocomposite are increased with increasing TiO₂ content and aromatic structure in the organic matrix due to their rigid characteristics. The transparency of the nanocomposite is increased with increasing TiO₂ content and dispersity. At the same loading of nanoparticles, the higher dispersity and the better transparency are due to the less extent of Rayleigh scattering. At 18 vol% (60 wt%) of TiO₂, the acetic acid modified TiO₂/poly(4-vinyl benzyl alcohol) nanocomposite has a refractive index of 1.73 and excellent transparency (>85% from 500 nm to 800 nm). The refractive index of the nanocomposite can be further increased to 1.77 by replacing aliphatic acetic acid modified TiO₂ with aromatic phenyl acetic acid modified TiO₂. The results of this work provide new knowledge and a new pathway to design a polymer based high refractive index material.