Long-range order in nanocellulose films and coatings for next generation materials

Aqueous dispersions of cellulose nanocrystals (CNCs) undergo a concentration-driven self-assembly which leads to chiral nematic (N*) structuring in dried coatings. The structural color provided by the N* order offer promise as a sustainable alternative to decorative iridescent, metallic, and shimmering effects. This dissertation studied the effects of the self-assembly on both structural and optical properties of dried films and coatings. The progress of the self-assembly in the dispersion state, altered through equilibration at different concentrations, was found to significantly impact the resulting dried coating, in terms of the sizes and distribution of the regions of N* order. The internal mechanical stresses that build up during the drying of CNC dispersions were quantified during coating formation and after ageing. A desirable stress reduction was achieved by mixing non-interacting plasticizing additives into the dispersion prior to coating formation. Of interest particularly in decorative applications, are the gradients in structural color at the edges of coated areas, known as coffee rings, which were examined in non-circular coatings. Lastly, an infiltration setup was investigated by introducing highly interacting compounds into CNC films, including proteins, which interfere with the self-assembly when mixed into the dispersion prior to drying. The findings of this dissertation are of interest to both technological and decorative implementations of structured cellulose nanocrystal coatings, and in the development of biocolloidal coatings.