Mesophase behaviour of 1, 2, 3-triazole-based nematic liquid crystals influenced by varying alkyl chains and halogen atom substitution. Issue 10 (9th August 2022)

• Record Type: Journal Article
• Authors: Xiong, Dan; Xiong, Xiaoping; Chen, Ziran; Yu, Wenhao; Feng, Chun; Chen, Hongmei; Ni, Hailiang; Wang, Biqin; Zhao, Keqing; Hu, Ping
• Is Part Of: Liquid crystals. Volume 49:Issue 10(2022)
• Page Start: 1261
• Page End: 1274
• Publication Date: 2022-08-09
• Subjects: Nematic phase -- click chemistry -- halogen atom substitution effect -- triazoles -- DFT calculations; Liquid crystals -- Periodicals; 548.905
• DOI: 10.1080/02678292.2022.2066731
• Languages: English
• ISSNs: 0267-8292

Abstract

ABSTRACT: To develop novel nematic-phase liquid-crystal (LC) materials with practical potential in optical and photovoltaic devices, the alkyl chain and halogen atom substitution in 1, 2, 3-triazole-based compounds were varied, and the effects on the mesophase behaviour were investigated. The 4-(4-propylcyclohexyl)phenyl 4-(1-alkyl-5-hydro/halo-1, 2, 3-triazol-4-yl)benzoate series 1 was successfully synthesised through tandem aerobic oxidative halogenation and click reaction via in situ activation. Except for 5-thiophene-1, 2, 3-triazole compound 1c-Th displaying no mesomorphism, the other compounds 1 form enantiotropic nematic mesophases, among which compounds 5-hydro-1, 2, 3-triazole 1c-H (C10) and 1d-H (C12) (long straight chain compounds) form two mesophases (smectic C phase and nematic phase). For 5-halo-1, 2, 3-triazole compounds 1c-X (× = halide), the mesomorphic temperature range was wider than for the corresponding compound 1c-H because of the effect of the halogen atom substituent on the triazole. Density functional theory (DFT) analysis showed that the structure-property relation for series 1c-X(H) could be defined by using the calculated dihedral angles, dipole moment, polarisability, and molecular electrostatic potential as parameters. Notably, introducing halogen atoms at the 5-position of 1, 2, 3-triazole can greatly broaden the mesogenic temperature range, ascribed to the weak intermolecular forces and large dipole moment in this class of compounds. GRAPHICAL ABSTRACT: uf0001