Induction, fixation and recovery of self-organized helical superstructures in achiral liquid crystalline polymer

The fixation, storage and self-recovery of chiral information in superstructures constructed by weak noncovalent bonds remain a big challenge in nature. Here, we describe a novel self-assembled system where the molecular chirality can be transferred and further stored into a helical superstructure. Based on achiral liquid crystalline polymers (LCPs), the twist between azobenzene (Azo) units in polymer side chains can be switched by the configuration or alkyl chain length of the introduced chiral dopant. Furthermore, the cross-linking strategy of polymer side chains was adopted to allow permanent memory of the induced helical superstructure after complete removal of the chiral dopant. Although the helical superstructure was temporarily destroyed by UV light irradiation, the stored chiral information enabled self-recovery of the previous helical chirality, without the need for any pre-existing chiral source. The chiral switching in the absence of chiral source is unprecedented and opens a new window for the design and application of chiral materials. A flexible chiral storage based on an achiral polymer system can be successfully achieved by chiral doping and covalent cross-linking.