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The Shape of Things To Come: The Formation of Modulated Nematic Mesophases at Various Length Scales
Author(s) -
Mandle Richard J.
Publication year - 2017
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.201701167
Subject(s) - mesophase , liquid crystal , materials science , phase (matter) , chirality (physics) , chemical physics , soft matter , helix (gastropod) , crystallography , polymer , twist , biphenyl , nanoscopic scale , chemistry , nanotechnology , symmetry breaking , physics , organic chemistry , composite material , chiral symmetry breaking , geometry , optoelectronics , ecology , quantum mechanics , colloid , mathematics , snail , nambu–jona lasinio model , biology
The twist–bend nematic (N TB ) phase is a recently discovered liquid‐crystalline phase that exhibits macroscopic chirality even when formed from achiral materials, and as such presents a unique testbed for studies concerning the spontaneous breaking of mirror symmetry in soft matter. It is primarily exhibited by materials for which the molecular structure is composed of two rigid aromatic units (such as biphenyl connected by a flexible spacer). The local structure of the N TB phase is nematic‐like—with molecules having an average orientational order but no positional order—with a nanoscale helix in which the pitch (i.e., the repeat distance of the helix) is of the order of several nanometres. A helix is chiral, and so the bulk N TB phase—in the absence of a biasing chiral environment—spontaneously separates into macroscopic domains of opposite handedness. After discussing the structure of this mesophase and its elucidation, this concept article presents the molecular factors that determine its incidence. The apparent dependency primarily on molecular shape and bend angle rather than particular functional group combinations manifests in this mesophase being exhibited on length scales far beyond those of simple liquid‐crystalline dimers, not only in oligomers and polymers, but also in aqueous suspensions of micron sized helical particles.