Diverse Side-Chain Transformation of High Refractive Index Methylthio-Substituted Poly(phenylene sulfide)s

Sulfur-containing polymers are useful in a wide range of optoelectronic applications, although their transparency and refractive indices are challenging to control precisely. Herein, we present a facile strategy for systematically modulating the optical properties of poly(2-methylthio-1,5-phenylene sulfide) (SMePPS) via post-polymerization modification. Initially, the selective side-chain oxidation of SMePPS yielded methyl sulfoxide-containing poly(phenylene sulfide) (PPS), exhibiting higher Abbe numbers, higher transparency, and ultrahigh refractive indices (nD = 1.75–1.80). Demethylation of SMePPS also yielded thiol-substituted PPS (SHPPS) with an even higher refractive index (nD = 1.84), owing to the intermolecular hydrogen bonding and the trace cross-linking effect. Furthermore, the film formability/stability of SHPPS was enhanced through copolymerization with methoxy-substituted PPS without comprising the refractive index properties. This facile post-polymerization modification strategy can achieve desirable tuning of optical properties in various sulfur-containing polymers.