Systematic Control of Sulfur Chain Length of High Refractive Index, Transparent Sulfur-Containing Polymers with Enhanced Thermal Stability

We herein report the preparation of high refractive index polymers (HRIPs) with enhanced thermal stability from the copolymerization of S₈ and divinylbenzene (DVB) in a single step through sulfur chemical vapor deposition (sCVD). Varying the process temperature in sCVD allowed for the preparation of a series of high sulfur content polymers which, in comparison to previously reported sulfur-derived polymers with similar compositions, displayed significantly enhanced solvent resistance, glass transition temperature (T_g), and thermal stability attributed to the absence of long polysulfide chains in the polymer matrix. The resulting HRIP films displayed high transmittance over the entire visible range while showing an unprecedentedly high T_g of 110 °C, which is one of the highest to date among HRIPs with refractive index (RI) exceeding 1.8 reported to date. With the combination of ultrahigh (>1.8) RI, thermal stability, and high T_g, the HRIPs can serve as compelling materials for advanced optical applications.