Entropy-driven self-assembly of chiral nematic liquid crystalline phases of AgNR@Cu₂O hyper branched coaxial nanorods and thickness-dependent handedness transition

The chiral nematic liquid crystalline phase (CNLCP) of noble metal nanorods induces a strong chiroptical response due to their intrinsic physical and chemical properties. Here, we demonstrate that the formation of CNLCP of Ag nanorods (AgNRs) originates from their bent-shape and is the result of purely entropic effects. The chirality of the liquid crystalline phase of AgNR@Cu₂O hyper branched coaxial nanorods (HBCNRs) can be switched from left-handed to right-handed by increasing Cu₂O thickness. It is proposed that the increase of coating thickness decreases the curvature of nanorods, which induces variation of the twist constant (K₂) and bend elastic constant (K₃). The increased thickness also changes the direction of director with respect to the helical axis. In addition, hydrogen bonds can break the CNLCP, which can be attributed to their stronger effection compared to van der Waals forces and electrostatic interactions. In contrast to the variation of coating thickness, the surface morphology, constituents of the hybrid building blocks and polarity of the solvents do not play important roles in the handedness transition of the liquid crystalline phase. Furthermore, the results presented here give insight into the structure–property relationship and our strategy provides guidance for the synthesis of other inorganic chiral suprastructures driven by entropic effects.