Synthesis of high refractive index and low-birefringence acrylate polymers with a tetraphenylethane skeleton in the side chain

We propose a new acrylate monomer that exhibits attractive optical properties, such as good transparency, high refractive index, low birefringence, desirable optical properties, and high thermal stability. Tetraphenylethane has four aromatic rings that bind without anisotropy. A polymer with this tetraarylethane structure is expected to exhibit a high refractive index and low birefringence. In this study, we synthesized two acrylate-based polymers via radical polymerization of the acrylate monomer and methacrylate derived from 1,1′,2,2′-tetrakis(4-hydroxyphenyl)ethane. We prepared transparent coatings of the polymers on a synthetic quartz plate via spin coating and measured their refractive indices using a prism coupler. Both of the polymers exhibited a high refractive index (1.60) as compared with common PMMA (1.49) and a low birefringence, which indicated that a tetraarylethane skeleton is the preferred candidate for suppressing the birefringence of a material.