Thioether-linked azobenzene-based twist-bend nematogens and their phase-transition behavior

Abstract

We synthesized symmetric azobenzene-based dimers (CN)AzoSnSAzo(CN) (n = 3, 5, 7, 9 and 11) and asymmetric (CN)AzoSnSCB (n = 3, 5, 7, 9 and 11), and evaluated their phase-transition behavior using polarized light optical microscopy and differential scanning calorimetry. Symmetric (CN)AzoSnSAzo(CN) dimers exhibited higher phase-transition temperature than those of asymmetric (CN)AzoSnSCB dimers for corresponding n. Asymmetric (CN)AzoSnSCB (n = 7 and 9) exhibited the twist-bend nematic (NTB) phase across a wide temperature range. The NTB phases were supercooled to room temperature to be vitrified.