Synthesis of High-Refractive-Index Oligomers Containing Bismuth in the Main Chain

Bismuth, a stable heavy element with high atomic polarizability, is a promising component for a class of high-refractive-index polymers (HRIPs). However, the potential of bismuth-containing polymers as HRIPs has yet to be fully explored. Here, two bismuth-containing oligomers were synthesized, incorporating triphenyl bismuth units and either sulfur or silicon atoms into the main chains. The resulting oligomers exhibited good solubility, and their spin-coated films showed highly optical transmittance. The refractive indices at 589 nm (nD) of these oligomers were 1.68 and 1.75, respectively. Notably, the latter is the highest value reported to date for bismuth-containing HRIPs.