Light-Controlled Supramolecular Helicity of a Liquid Crystalline Phase Using a Helical Polymer Functionalized with a Single Chiroptical Molecular Switch

Abstract

Control over the preferred helical sense of a poly(n-hexyl isocyanate) (PHIC) by using a single light-driven molecular motor, covalently attached at the polymer's terminus, has been accomplished in solution via a combination of photochemical and thermal isomerizations. Here, we report that after redesigning the photochromic unit to a chiroptical molecular switch, of which the two states are thermally stable but photochemically bistable, the chiral induction to the polymer's backbone is significantly improved and the handedness of the helical polymer is addressable by irradiation with two different wavelengths of light. Moreover, we show that the chiral information is transmitted, via the macromolecular level of the polyisocyanate, to the supramolecular level of a lyotropic cholesteric liquid crystalline phase consisting of these stiff, rodlike polymers. This allows the magnitude and sign of the supramolecular helical pitch of the liquid crystal film to be fully controlled by light.

Deracemization of Axially Chiral Nicotinamides by Dynamic Salt Formation with Enantiopure Dibenzoyltartaric Acid (DBTA)

“…In the cases of 1b and 1c, removal of the solvent by evaporation led to a viscous oil, and deracemization was not observed (entries 3 and 6). In previous experiments involving deracemization by salt formation in the solution phase, it was demonstrated that external chiral stimuli induced a helical sense in a dramatically optically active helical polymer or oligomer [49][50][51][52][53][54]. In our experiment, the axial chirality of 1a-c could not be controlled in the solution phase because the chiral acid in the salt was located far from the axial chiral auxiliary.…”

Supramolecular Chirality in Dynamic Coordination Chemistry

“…such as small organic molecules [13][14][15][16][17][18][19], polymers [20][21][22][23], metamaterials [24], and assemblies [25][26][27][28], have been developed for chirality induction and switching in response to external stimuli, more sophisticated systems are required to mimic natural systems.…”

The transformation of chiral signals into macroscopic properties of materials using chirality-responsive polymers

“…In general, UV irradiation or circularly polarized light (CPL) is introduced as a light stimulus to mediate and enhance the chiral effects of materials. In the exquisite study presented by Pijper et al 37 in 2008, UV light was utilized as a stimulus to mediate the chirality of a helix. The authors attached a chiroptical switching molecule at the end of a poly(n-hexyl isocyanate) chain that worked as a light-driven motor.…”