All-Bio-Based Flexible Chiral Nematic Cellulose Nanocrystal Films

Cellulose nanocrystal (CNC)-based photonic crystals have attracted significant attention in the field of intelligent sensing due to their environmental response characteristics. However, traditional CNC photonic films are hindered by high brittleness and delayed humidity response, which severely limit their practical application in dynamic deformation scenarios and rapid humidity monitoring. To overcome these limitations, here, we present a hydrogen-bonding synergy strategy that integrates CNC, hydroxypropyl cellulose, and d-glucose into a ternary network, enabling the preparation of a fully biobased photonic film with enhanced mechanical flexibility and ultrafast humidity responsiveness. Remarkably, the optimized composite film exhibits an elongation at break of 25.3 ± 2.5%, a 79-fold improvement over pure CNC. This film demonstrates a broad humidity-responsive optical shift across the relative humidity range of 32-86%. In addition, the obtained composite films are fully biodegradable and biocompatible due to their renewable components.