Electro-switchable cellulose nanocrystal films with chiroptical properties.

A series of stable electro-switchable cellulose nanocrystal (CNC) films is fabricated by the covalent functionalization of preassembled chiral nematic CNC substrates with electro-active molecules. Through this approach, we anchor siloxy-group-containing viologens (SV) to the surface of CNCs in a preformed film. Unlike conventional premixing strategies that typically disrupt chiral self-assembly of CNCs, this method produces films that retain the structural color and chiroptical properties of the chiral nematic CNC substrate, while exhibiting stable electrochromic performance. Our films show responses not only to voltage but also to light, heat and alkaline environments, demonstrating their potential as multi-responsive materials. This methodology extends beyond chiral nematic CNCs to other nanostructured substrates such as mesoporous chiral nematic silica. The resulting materials show potential for smart optical applications, including dynamic information display and security technologies, enabling tunable visibility and encryption/decryption technologies.