High Refractive Index Copolymers from Aromatic Heterocycle‐Based Vinyl Sulfides and Phthalimide/Maleimide Derivatives

Abstract

AbstractHerein, the rational design and facile synthesis of high‐refractive‐index copolymers with good optical transparency and tunable thermal stability using aromatic heterocycle‐based vinyl sulfides via conventional radical copolymerization is presented. 2‐Thiazolylvinylsulfide (2TVS), 1,3,4‐thiadiazolylvinylsulfide (1,3,4‐TVS), 3‐methylimidazolylvinylsulfide (3MIVS), and 5‐methlthio‐1,3,4‐thiadiazolylvinylsulfide (MeSTVS) are selected to enhance the refractive index, and N‐vinylphthalimide (NVPI) and N‐phenylmaleimide (NPMI) are chosen as comonomers to achieve improved transparency and thermal stability while maintaining the refractive index. The sulfur, ─C═N─, and imide contents in the copolymers are varied by adjusting the monomer structures and their compositions, and their effects on the refractive index, Abbe number, and optical and thermal properties are investigated. The MeTVS monomer in poly(MeSTVS) and poly(MeSTVS‐co‐NVPI) contained three sulfur atoms and two ─C═N─ units; consequently, these polymers exhibit excellent refractive indices in the 1.7139–1.6567 range at 589 nm, Abbe numbers between 19.1–29.1, good transparency (>90% at 400 nm), and tunable thermal properties (Tg = 49–138 °C, Td10 = 244–268 °C). Optically transparent poly(1,3,4‐TVS‐co‐NVPI) films (>95% at 400 nm) with improved thermal stability (Tg = 89–175 °C, Td10 = 251–301 °C) are obtained while maintaining a relatively high refractive index (1.6662–1.6752).