Poly(phenylene sulfide) (PPS) is an engineering plastic with high thermal stability, crystallinity and chemical resistance used in automotive and electronic applications. While PPS is generally produced via polycondensation of p-dichlorobenzene and Na₂S (Philips method), our group reported oxidative polymerization of diphenyl disulfide (DPS) as a novel PPS synthesis. We also found this oxidative polymerization gave various PPS derivatives with functional groups, due to its Friedel-Crafts type polymerization behavior controlled by HOMO/LUMO levels of reactive species. These PPS derivatives could be applied to high refractive index transparent thermoplastics derived from its amorphous and sulfur-rich backbone. Herein, we report the synthesis of alkoxyl-substituted PPSs as new high refractive index polymers, and further post-functionalization for enhancing their refractive indices.
Poly(2-methoxy-1,4-phenylenesulfide) (OMePPS) was synthesized via oxidative polymerization of 2-methyl-substituted DPS, which gave an amorphous polymer with suitable glass transition temperature (~ 125 °C), high transparency (> 75%T) and high refractive index properties (n_D = 1.73, ν_D = 22). Various post-functionalization of OMePPS was further conducted by taking advantage of reactive methoxy groups. By introducing phenolic groups through demethylation, ultrahigh refractive index with n_D over 1.8 could be accomplished due to the enhancement of intermolecular hydrogen bonds between side chains.

Seigo Watanabe

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