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

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 pi-pi stacking between aromatic groups from LCs and TPE groups and the sigma-pi 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.

Automated summary

This study provides a systematic exploration of chiral amplification of chiral aggregation induced emission (AIE) molecules in liquid crystals (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. The direct visualization using AFM imaging revealed that chiral AIE molecules self-assembled into helical fibers to serve as the helical template for LCs to bind, forming co-assemblies with morphologies of pearled necklaces or thick rods. Theoretical calculations suggested that chiral AIE molecules were packed into left-handed helical fibers with empty space between neighboring molecules, providing binding sites for LCs.