Surface modification of cellulose nanocrystals (CNCs) is often required to improve their compatibility with other formulation components in a range of applications. Past methods to tune CNC hydrophobicity, colloidal/thermal stability, or rheological properties have been developed but generally require the use of harsh chemicals, complex chemistries, multiple steps and tedious clean-up. Presented here, is an in situ modification route to tailor CNC properties through the precipitation of oligosaccharides during CNC production. The novel modification route leverages the selective solubility of oligosaccharides, which are soluble at low pH (during the CNC acid hydrolysis) yet become insoluble and precipitate onto CNC surfaces upon dilution with water. In this proof-of-principle work, elemental analysis, conductometric titrations, zeta potential and gel permeation chromatography were used to confirm successful CNC modification with cellulose phosphate oligosaccharides. The effects of surface oligosaccharides on CNC performance were assessed through thermogravimetric analysis, rheology and quartz crystal microgravimetry. Oligosaccharide-coated CNCs had higher surface charge densities, lower water adsorption capacities and lower viscosities than their unmodified counterparts. CNC surface coverage was tuned by controlling the oligosaccharide degree of polymerization. This easily-scaled, simple and green alternative for CNC surface modification opens the door for expanded CNC functionality and applications and the in situ nature may allow it to be implemented in CNC manufacturing facilities without alterations to existing production lines.

Surface modification of cellulose nanocrystals in situ during production using oligosaccharide precipitation

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.