Light-Directed Dynamic Chirality Inversion in Functional Self-Organized Helical Superstructures

• Published in: Angewandte Chemie International Edition Vol. 55; no. 9; pp. 2994 - 3010
• Main Authors: Bisoyi, Hari Krishna, Li, Quan
• Format: Journal Article
• Language: English
• Published: Germany Blackwell Publishing Ltd 24.02.2016; Wiley Subscription Services, Inc
• Edition: International ed. in English
• Subjects: Assemblies; chiral liquid crystals; Chirality; Cholesteric liquid crystals; Circular polarization; Crystals; Dopants; Dynamical systems; External stimuli; Functional anatomy; Guidelines; Handedness; helix inversion; Host-guest materials; Light; light-driven systems; Liquid crystals; Macromolecules; Materials selection; Molecular machines; Molecular motors; molecular switches and motors; Morphology; Nematic crystals; Polarized light; Polymers; Stimuli; Superstructures; Supramolecular compounds; Switches; Throwing; helix inversion; molecular switches and motors; chiral liquid crystals; light-driven systems
• ISSN: 1433-7851; 1521-3773; 1521-3773
• DOI: 10.1002/anie.201505520

Helical superstructures are widely observed in nature, in synthetic polymers, and in supramolecular assemblies. Controlling the chirality (the handedness) of dynamic helical superstructures of molecular and macromolecular systems by external stimuli is a challenging task, but is of great fundamental significance with appealing morphology‐dependent applications. Light‐driven chirality inversion in self‐organized helical superstructures (i.e. cholesteric, chiral nematic liquid crystals) is currently in the limelight because inversion of the handedness alters the chirality of the circularly polarized light that they selectively reflect, which has wide potential for application. Here we discuss the recent developments toward inversion of the handedness of cholesteric liquid crystals enabled by photoisomerizable chiral molecular switches or motors. Different classes of chiral photoresponsive dopants (guests) capable of conferring light‐driven reversible chirality inversion of helical superstructures fabricated from different nematic hosts are discussed. Rational molecular designs of chiral molecular switches toward endowing handedness inversion to the induced helical superstructures of cholesteric liquid crystals are highlighted. This Review is concluded by throwing light on the challenges and opportunities in this emerging frontier, and it is expected to provide useful guidelines toward the development of self‐organized soft materials with stimuli‐directed chirality inversion capability and multifunctional host–guest systems. Photoisomerizable chiral molecular switches or motors as guests induce chirality into achiral nematic liquid crystals and enable light‐driven chirality inversion of the resulting cholesteric liquid crystals (CLCs). This Review describes the recent developments in the rational design of chiral guests with the capability for light‐directed chirality inversion of CLCs.