Synthesis of colorless and high-refractive-index sulfoxide-containing polymers by the oxidation of poly(phenylene sulfide) derivatives

Highly refractive, thermostable, and transparent poly(phenylene sulfide) (PPS) derivatives partially including SO bonds were reported. The polymers were prepared by m-chloroperbenzoic acid (mCPBA) oxidation of the corresponding PPS derivatives, affording sulfoxide or sulfone-containing polymers with high oxidation selectivity. After the oxidation, the transparency and glass-transition temperature (T_g) of the polymers enhanced while maintaining their high refractive indices (n_D = 1.66–1.71), owing to the introduction of rigid sulfoxide/sulfone moieties. This bleaching of the bulk films was due to the loss of the lone pairs on the sulfur atom in the sulfide bonds through the formation of the SO bonds, which led to a smaller conjugation length and weaker absorption in the near-UV region. From the viewpoint of both molar refraction and molecular volume, incorporating the sulfoxide moiety is the best way to enhance transparency and maintain a suitable T_g with a high refractive index.