We present bioinspired crack-free monolithic chiral nematic films in the capillary confinement through a unidirectional flow of cellulose nanocrystals (CNC) with enhanced hydrogen bonding.  To achieve the uniform long-range nanocrystals organization during drying, we employed tunicate-inspired hydrogen-bonding-rich 3,4,5-trihydroxyphenethylamine hydrochloride (TOPA) for physical crosslinking of nanocrystals and polyethylene glycol (PEG) as a relaxer of internal stresses in the vicinity of the capillary surface.  The CNC/TOPA/PEG film is self-assembled into a left-handed chiral structure parallel to flat walls, and films displayed herringbone organization across the interfacial region.  The resulting ultrathin films also exhibit higher mechanical performance than CNC/PEG film with reduced cracks compared to pure CNC films.  The chiral nematic ordering of modified TOPA-PEG-CNC material spreads through the entire thickness of robust monolithic films and across centimeter-sized surface areas, facilitating consistent, vivid interference colors, and enhanced circular polarization. Overall, we demonstrate a minimal amount of TOPA molecules in the CNC/TOPA/PEG composite can enhance the ultimate tensile strength and toughness, control the optical reflection peak position, and improve circular polarization.

Monolithic bioinspired chiral nematic organization of cellulose nanocrystals with enhanced hydrogen bonding

ACS Fall 2021

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