Structure Color Tuners of Cholesteric Cellulose Nanocrystal

The broad utility of cellulose nanocrystals (CNCs) as green, vivid, and long-term photonic films is restricted by their coloration instability and limited gamut. Herein, four polyols, two monosaccharides, two organic acids, and four amino acids were doped into a CNC for a detailed structure and color hue investigation. The results show that polyols and saccharides bearing neural multihydroxyl groups promoted a doping-amount-dependent red-shift reflection. Polyols were also found to improve the flexibility of CNCs as effective plasticizers. Organic tartaric or malic acid showed effects on the overall blue shift although a switch from blue shift to red shift happened at a doping amount of 8 wt %. Nevertheless, amphoteric amino acids with multifunctional groups show limited regulating effects due to their poor compatibility and complicated interactions with CNCs. Therefore, acidic or alkaline functional groups, the isoelectric point, a compatible saccharide ring, the molecular weight, and crystallization of dopants are crucial factors for tuning the structure and properties of CNCs.