Design, synthesis and characterization of high refractive index aromatic polyesters containing fluorene and thioether groups

9,9-bis(4-hydroxyphenyl)fluorene (BPF) is a highly structurally symmetric bisphenol with excellent optical properties of low birefringence and high refractive index, however, the glass transition temperature ( Tg) of its polyester is high ( Tg>300°C), which makes it difficult to be thermally processed and limits its application. On the other hand, 4,4′-Thiobis (2-methylphenol) (T2MP) has a flexible thioether group, its introduction not only brings high refractive index, but also can appropriately reduce the Tg of the polymer. Therefore, by combining the advantages of both of them, we prepared aromatic polyesters with high refractive index and stabilization. This study provides a route that can appropriately reduce Tg without loss of refractive index.