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Ether‐ and Thioether‐Linked Naphthalene‐Based Liquid‐Crystal Dimers: Influence of Chalcogen Linkage and Mesogenic‐Arm Symmetry on the Incidence and Stability of the Twist–Bend Nematic Phase
Author(s) -
Arakawa Yuki,
Ishida Yuko,
Tsuji Hideto
Publication year - 2020
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201905208
Subject(s) - mesogen , thioether , liquid crystal , crystallography , dimer , materials science , ether , phase (matter) , stereochemistry , chemistry , organic chemistry , polymer chemistry , liquid crystalline , optoelectronics
The twist–bend nematic (N TB ) phase with a heliconical nanostructure of the local director generating symmetry breaking by achiral bent‐shaped molecules is a hot topic of current liquid‐crystal science. As opposed to the most common methylene‐linked dimers, this study demonstrates chalcogen ether‐ and/or thioether‐linked 6‐(4‐cyanophenyl)‐2‐naphthyl‐based liquid‐crystal dimers with symmetric and asymmetric π‐conjugated mesogenic‐arm structures that exhibit the N TB phase. Although the symmetric bis(ether)‐linked dimer exhibits only the conventional nematic (N) phase, the asymmetric bis(ether)‐linked dimer can form the N TB phase. All thioether‐linked dimers form the N TB phase, wherein the dimers with asymmetric arms vitrify in the N TB phase on cooling to room temperature. The phase transitions are discussed in terms of the chalcogen linkage combination, mesogenic‐arm symmetry, and spacer length. It is revealed that thioether‐linked dimers based on asymmetric π‐conjugated mesogenic arms with terminal cyano groups are highly beneficial for the realization of materials that form a wide range of N TB phases and glassy N TB states at room temperature.