Controlled Synthesis of Cyclic-Helical Polymers with Circularly Polarized Luminescence

Cyclic polymers attract attention because of their endless structure and unique properties, which differ from the linear analogs. However, the synthesis of cyclic polymers is difficult and prohibits their functions and applications. In this study, we reported chiral cyclic Pd^II -catalysts that initiate a living ring-expansion polymerization of isocyanides, yielding a single-handed cyclic-helical poly(phenyl isocyanide), with predictable molecular weight (M_n ) and low dispersity (M_w /M_n ), in good yield. Using this method, cyclic bottlebrush polymers were prepared via the grafting-onto strategy. The cyclic topology was confirmed using various spectroscopic data and atomic force microscope observation. Moreover, the cyclic polymer brushes, comprising of a one-handed helical backbone, showed interesting photoluminescence and circularly-polarized luminescence.