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 (T-g) of its polyester is high (T-g>300 degrees 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 T-g 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 T-g without loss of refractive index. Graphical Abstract