By utilizing optically active liquid crystals as sites for reactions, researchers have made significant strides in the living polymerization of polymers featuring aligned helical forms. During this process, optically inactive monomers take on chiral (mirror-image) configurations within the liquid crystals as they develop, leading to the formation of optically active polymers. This accomplishment is a groundbreaking advancement in both asymmetric chemistry and polymer science.
Polyisocyanides are specialized polymers known for their helical structures, where the direction of the helix’s twist (either right-handed or left-handed) can be manipulated using catalysts meant for crafting chiral molecules. This ability enables polyisocyanides to display optical characteristics such as circular dichroism and optical rotation, thus becoming stable, optically active materials.
The research team successfully created optically active conducting polymers from non-optical monomers utilizing physical methods instead of chemical ones, employing a liquid crystal reaction environment as an external setting. For the first time, they accomplished asymmetric (chiral) living polymerization of optically active polyisocyanides using liquid crystals featuring chiral (mirror-image isomer) structures as solvents.
Measurements of circular dichroism in the produced polyisocyanides verified their optical activity, resulting from their helical arrangements. Furthermore, the liquid crystal utilized in this reaction displayed properties associated with the twisted-bend nematic phase—a newly identified state that has garnered significant interest in liquid crystal research. Discovering this twisted-bend nematic liquid crystal within a polymer is a remarkable achievement in the study of liquid crystals.
This process is similar to the way amino acids with chiral forms grow enzymatically in living organisms, resulting in the creation of proteins with helical structures. Therefore, it shows promise as a biomimetic technology—a domain that seeks to imitate and capitalize on the functional strategies of living systems.
This research was supported by JSPS Grants-in-Aid for Scientific Research, Grant Number 20K05626 (H. Goto).
