Thioether-linked benzylideneaniline-based twist-bend nematic liquid crystal dimers: Insights into spacer lengths, mesogenic arm structures, and linkage types

Abstract

The first examples of thioether-linked benzylideneaniline-based liquid crystal dimer homologues, namely symmetric N-(4-cyanobenzylidene)aniline-based homologues [i.e., (CN)BASnSBA(CN)] and unsymmetric N-(4-cyanobenzylidene)aniline- and 4-cyanobiphenyl-based homologues [i.e., (CN)BASnSCB] possessing different alkylene spacers (CnH2n, n = 3, 5, 6, 7, 9, and 11) were synthesized and characterized. The odd-n (CN)BASnSBA(CN) and (CN)BASnSCB homologues formed twist-bend nematic (NTB) phases below the temperatures of conventional nematic (N) phases upon cooling. Remarkably, the NTB phases of the unsymmetric (CN)BASnSCB (n = 3, 5, 7, and 9) homologues were supercooled below room temperature and vitrified as the NTB glass phases. The impacts of the N-(4-cyanobenzylidene)aniline structure on the LC phase-transition behavior were revealed in terms of the spacer lengths, mesogenic arm structures (or symmetry), and linkage types.