Direct Visualization of Chiral Amplification of Chiral Aggregation Induced Emission Molecules in Nematic Liquid Crystals

Abstract

Chiral amplification in liquid crystals (LCs) is a well-known strategy. However, current knowledge about the underlying mechanism was still lacking; in particular, how it was realized at the nano scale still remained to be revealed. Here, we provide systematical exploration of chiral amplification of chiral aggregation induced emission (AIE) molecules in LCs from direct visualization of their co-assemblies at the nano scale to theoretical calculation of the molecular packing modes on a single molecular level. Using AFM imaging,we directly visualized the co-assembly formed by chiral AIE molecules/LCs at the nano scale: the chiral AIE molecules self-assembled into helical fibers to serve as the helical template for LCs to bind, while the LCs helically bound to the helical fibers to form the co-assembly, giving the morphology of pearled necklaces or thick rods. Theoretical calculation suggested that chiral AIE molecules were packed into left-handed helical fibers with a large volume of empty space between neighboring molecules, which provided the binding cites for LCs. Structural analysis showed that the π–π stacking between aromatic groups from LCs and TPE groups and the σ–π hyperconjugation between LC aromatic groups and cholesterol aliphatic groups play an important role in stabilizing the binding of LCs in the confined space on the surface of the helical assemblies.

Frontiers in circularly polarized luminescence: molecular design, self-assembly, nanomaterials, and applications

“…All of these silole derivatives exhibited obvious AIE characteristics as well as good CPL property when aggregating into chiral superstructures. Molecules 20-23 are chiral TPE derivatives bearing an L-leucine methyl ester moiety [54], cholesterol periphery [55], BINOL-based boronic ester [56], and BINOL-based dihexyl diether [57], respectively. These TPE-derivated AIE-CPL systems with various point, axial and planar chirality have the advantages of facile synthesis, high emission efficiency.…”

Engineering Achiral Liquid Crystalline Polymers for Chiral Self-Recovery

“…Besides, the typical fingerprint textures of the chiral nematic phase were clearly observed when undergoing an appropriate annealing process ( Figure S9 ). It can be speculated that the orientation of the mesogens in polymer side chains (PBs or CNBs) are slightly twisted with respect to their neighbors under the command of chiral dopants, leading to a long-range helical periodic superstructure [ 43 ].…”

Circularly polarized luminescent self‐organized helical superstructures: From materials and stimulus‐responsiveness to applications

“…Tang et al explored the coassemblies of chiral AIE molecules and LCs at the nanoscale for the first time (Figure 2B). [68] The TPE derivatives kept CD silent in tetrahydrofuran solution, even in a suspension. By doping AIEgens into 5CB, considerably enhanced CD and CPL signals were detected.…”