Multifunctional cellulose nanocrystal structural colored film with good flexibility and water-resistance.

Chiral nematic cellulose nanocrystal (CNC) structural colored materials are the focus of extensive research in recent years on account of their unique helical structure and excellent optical properties. However, the general weak mechanical properties and poor water-resistance of CNC limit its utility. Here, we fabricated highly flexible, water-resistant chiral nematic CNC/Poly(ethylene glycol) diacrylate(PEGDA) composite films, which was realized by co-assembling CNC and PEGDA precursor then via UV curing to construct a three-dimensional crosslinking network. Due to the water stimulus-responsive feature of the CNC and PEGDA, the CNC/PEGDA (8/2) composite film could be used as a water-content detector, photonic paper. In addition, it could produce different crosslinking degrees by coating the PEGMA solution or not, which could be applied to an anti-counterfeit label. The composite film with excellent stability of cycles is expected to be a promising candidate in optical sensors, display, and security fields.