Photoresponsive and Polarization‐Sensitive Structural Colors from Cellulose/Liquid Crystal Nanophotonic Structures

Cellulose nanocrystals (CNCs) possess the ability to form helical periodic structures that generate structural colors. Due to the helicity, such self‐assembled cellulose structures preferentially reflect left‐handed circularly polarized light of certain colors, while they remain transparent to right‐handed circularly polarized light. This study shows that combination with a liquid crystal enables modulation of the optical response to obtain light reflection of both handedness but with reversed spectral profiles. As a result, the nanophotonic systems provide vibrant structural colors that are tunable via the incident light polarization. The results are attributed to the liquid crystal aligning on the CNC/glucose film, to form a birefringent layer that twists the incident light polarization before interaction with the chiral cellulose nanocomposite. Using a photoresponsive liquid crystal, this effect can further be turned off by exposure to UV light, which switches the nematic liquid crystal into a nonbirefringent isotropic phase. The study highlights the potential of hybrid cellulose systems to create self‐assembled yet advanced photoresponsive and polarization‐tunable nanophotonics. A polarization‐sensitive and photoresponsive nanophotonic system based on structural colors that are generated by cellulose nanocrystal films and modulated by a birefringent liquid crystal coating is presented. Intense structural colors are appealingly varied by altering the handedness of the illuminating circularly polarized light. The system is further made photoresponsive using a UV‐light‐sensitive liquid crystal mixture.