Synthesis and characterization of phosphorus- and sulfur-containing aromatic polyimides for high refractive index

This paper represent synthesis and characterization of highly refractive polyimides containing phosphine oxide and thioether unit in the polymer chains. The polyimides (PIs) were synthesized by the conventional two-step polycondensation from several aromatic dianhydrides, such as 4,4'-[p-thiobis(phenylenesulfanyl)]diphthalic anhydride (3SDEA), 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), 4,4′-oxydiphthalic anhydride (ODPA) and pyromellitic dianhydride (PMDA) with the BATPO. The polymers exhibited high thermal properties such as glass transition temperature (>212 °C), and 5% weight loss temperature at >502 °C under nitrogen. The polymers also showed good optical properties, including high optical transparency in the visible region, a low birefringence and high refractive indices at 637 nm.228