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 (SNAr) reactions involving monomers with the P═S groups or an SNAr 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.
Hifumi et al. (Tue,) studied this question.