Molecular Structure and Properties of Sulfur-Containing High Refractive Index Polymer Optical Materials

High refractive index polymers (HRIPs) are widely used in lenses, waveguide, antireflective layer and encapsulators, especially the advanced fields of augmented/virtual reality (AR / VR) holographic technology and photoresist for chip manufacturing. In order to meet the needs of different applications, the development of HRIPs focuses not only on the increase in refractive index but also on the balance of other properties. Sulfur-containing high refractive index polymers have received extensive attention from researchers due to their excellent properties. In recent years, not only ultrahigh refractive index sulfur-containing polymers have been continuously developed, but also low dispersion, low birefringence, high transparency, good mechanical properties, and machinability have been studied. The design of HRIPs is generally based on formulas and existing experience. In fact, molecular structure and properties are closely related. Mastering the structure-property relationship helps researchers to develop high refractive index polymer materials with balanced properties. This review briefly introduces the preparation methods of sulfur-containing high refractive index polymers, and summarizes the structure-property relationship between the sulfur-containing molecular structure and optical properties, mechanical properties, thermal properties, etc. Finally, the important role of synergistic effect in the synthesis of HRIPs and the prospect of future research on HRIPs are proposed.

Facile synthesis of telechelic poly(phenylene sulfide)s by means of electron-deficient aromatic sulfonium electrophiles

We report the facile synthesis of telechelic poly(phenylene sulfide) (PPS) derivatives bearing functional groups at both termini. α,ω-Dihalogenated dimethyl-substituted PPS were obtained in high yield with a high degree of end-functionalization by using soluble poly(2,6-dimethyl-1,4-phenylenesulfide) (PMPS) and 4,4'-dihalogenated diphenyl disulfide (X-DPS, X = Cl, Br) as a precursor and an end-capping agent, respectively. Further end-functionalization is achieved through cross-coupling reactions; particularly, the Kumada-Tamao cross-coupling reaction of bromo-terminated telechelic PMPS and a vinylated Grignard reagent afforded end-vinylated PMPS with thermosetting properties. This synthetic approach can be applied to the preparation of various aromatic telechelic polymers with the desired structures and functionalities.

Transcending the Trade-off in Refractive Index and Abbe Number for Highly Refractive Polymers: Synergistic Effect of Polarizable Skeletons and Robust Hydrogen Bonds

High-refractive-index polymers (HRIPs) are attractive materials for the development of optical devices with high performances. However, because practical components and structures for HRIPs are limited from the viewpoint of synthetic techniques, it has proved difficult using traditional strategies to enhance the refractive index (RI) of HRIPs to more than a certain degree (over 1.8) while maintaining their visible transparency. Here, we found that poly(phenylene sulfide) (PPS) derivatives featuring both methylthio and hydroxy groups can simultaneously exhibit balanced properties of an ultrahigh RI of n _D = 1.85 and Abbe number of ν_D = 20 owing to the synergistic effect of high molar refraction and dense intermolecular hydrogen bonds (H-bonds). This brand new strategy is anticipated to contribute to the development of HRIPs displaying ultrahigh RI with adequate Abbe numbers beyond the empirical n _D-ν_D threshold, which has not been achieved to date.