Chiral Reaction Field with Thermally Invertible Helical Sense that Controls the Helicities of Conjugated Polymers

Abstract A chiral reaction field with thermally invertible helical sense enables control of the helicity of the reaction product, which is a central challenge in asymmetric synthesis that has yet to be overcome. A novel chiral compound comprising two types of chiral moieties with opposite helicities and temperature dependences is synthesized; this compound is added as a chiral dopant to a mixture of nematic liquid crystals to prepare a chiral nematic liquid crystal (N*‐LC). The N*‐LC containing the chiral dopant exhibits thermally invertible helicity to yield left‐ and right‐handed helical senses at low and high temperatures, respectively. Interfacial polymerization of acetylene is achieved in the N*‐LC by modulating the temperature. Helical polyacetylenes (H‐PAs) that are synthesized at low (−12 °C) and high (28 °C) temperature show right‐ and left‐handedness, respectively, in terms of the fibrils, fibril bundles, and spiral morphology. In addition, the helical sense of H‐PA is opposite that of the N*‐LC because of the peculiar polymerization mechanism for acetylene in the N*‐LC. The current N*‐LC is the first chiral reaction field that has not only the thermally invertible helical sense but also the chemical functions and stability needed to serve as the medium for polymer reactions.