Structures and Optical Properties of Resins Containing Several Carboxylic Acids Neutralized with Barium Ion

Abstract

Monomer composites containing an aromatic carbozylic acid and methacrylic acid (or acrylic acid) partially neutralized with a barium compound showed good solubility in chlorostyrene at high barium ion concentrations, unlike composites containing only one carboxylic acid. The improved solubility was due to the presence of an ionic crosslink composed of the aromatic carboxylate ion and methacrylate (acrylate) ion bridged with a barium ion, which provided an effective structure for depressing the growth of ionic associations. The bulky structure also enabled resins to maintain their transparency after being copolymerized with chlorostyrene. The refractive indices and Abbe numbers of the resins were measured and differences in optical properties between various carboxylic acids were evaluated according to (Ru)/Mu and the density in the Lorentz-Lorenz equation, where (Ru) and Mu are the unit molar refraction and residue molecular weight, respectively. The resins with acrylic acid had a higher refractive index without decrease of the Abbe number at the same barium content than those with methacrylic acid, due to the effect of the former on increased resin density. The introduction of an aromatic acid having a high molar refraction value led to increase of the refractive index, but its effect on the increase was small, because it caused a drop in resin density.