Chiral Reaction Field with Thermally Invertible Helical Sense that Controls the Helicities of Conjugated Polymers. Issue 12 (6th February 2020)

• Record Type: Journal Article
• Authors: Akagi, Kazuo; Yamashita, Tomohiro; Horie, Keita; Goh, Munju; Yamamoto, Masaharu
• Is Part Of: Advanced materials. Volume 32:Issue 12(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-02-06
• Subjects: asymmetric reaction field -- chiral nematic liquid crystals -- control of helical sense -- helical conjugated polymers -- temperature‐induced helical inversion; Materials -- Periodicals; Chemical vapor deposition -- Periodicals; 620.11
• DOI: 10.1002/adma.201906665
• Languages: English
• ISSNs: 0935-9648

Abstract

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. Abstract : A novel chiral compound comprising two types of chiral moieties with opposite helicities and temperature dependences is synthesized and added as a chiral dopant to a mixture of nematic liquid crystals to prepare a chiral nematic LC (N*‐LC). The N*‐LC exhibits left‐ and right‐handed helical senses at low and high temperatures, respectively, which allows the production of helicity‐controlled helical‐conjugated polymers.