Synthesis of Aromatic Poly(Thioether)s with Phosphine Sulfide Groups for High-Refractive-Index Materials

High-refractive-index polymers are essential for developing high-performance optical components in modern devices, and one effective approach to designing such materials is to incorporate functional groups containing heavy atoms and/or multiple bonds into polymer structures in higher contents. In the present study, we developed a series of aromatic poly-(thioether)-s incorporating phosphine sulfide (PS) groups, which contain relatively heavy heteroatoms and multiple bonds between them, for high-refractive-index materials. The polymers were synthesized via nucleophilic aromatic substitution (S(N)Ar) reactions involving monomers with the PS groups or an S(N)Ar reaction involving a monomer with a phosphine oxide (PO) group and subsequent conversion of the PO to PS groups using Lawesson's reagent. The poly-(thioether)-s containing the PS groups achieved higher refractive indices, ranging from 1.725 to 1.757 at 589 nm, than the corresponding polymers containing either the PS or thioether moieties. The refractive indices of these poly-((thio)-ether)-s containing the PO or PS groups positively correlate with the heavy heteroatom (S and P) content of the polymers, indicating that the combination of the PS groups and the thioether linkages effectively enhances the refractive indices of the polymers. The above results highlight the potential of the PS group for expanding the structural diversity of polymeric optical materials.