Multiapproach for Structural Colour Modulation in Electrodeposited Cellulose Nanocrystals Films

Cellulose Nanocrystals (CNCs) have a natural ability to self-organize into a chiral nematic liquid crystal phase with a helical arrangement. This characteristic can be preserved in dry CNC films, resulting in iridescent colors and interesting photonic properties. These properties include the selective reflection and transmission of right- and left-handed circular polarized light (RCPL and LCPL, respectively). CNCs naturally develop into a left-handed structure, which only reflects LCPL. Therefore, there is a need for structures capable of reflecting RCPL to access both polarization states.<br/>This work demonstrates how the reflected wavelength of CNCs electrodeposited layers can be modulated across the entire visible light range through passive and dynamic stimulation. The photonic bandgap is modulated trough ions exchange and by the adsorption of humidity. In addition, multilayer electrodeposited CNCs structures with the ability to reflect in both left-handed circularly polarized light (LCPL) and right-handed circularly polarized light (RCPL) channels were studied using polypropylene tape as retardation plates. This method allows for a wide variety of colors in LCPL and RCPL to be obtained, depending on the number of layers and the initial photonic bandgap conditions of the CNCs films. Additionally, the birefringence is studied and predicted through reverse engineering in stress-induced birefringent tapes, particularly polypropylene. The results demonstrate the potential of CNCs multilayer structures to be applied in photonics, stereoscopic imaging, sensing, and information processing.