(666c) Hydrolytically Stable Films from 3-Aminopropyl Triethoxysilan (APTES) Modified Cellulose Nanocrystals

Commercially available sulfuric acid hydrolyzed cellulose nanocrystals (CNCs) are extensively explored as advanced functional materials. They possess high dispersibility in water due to having sulfate half ester groups on their surface, which enables easy processability. However, water dispersibility also prevents the use of CNC films in applications requiring hydrolytic stability. To address this issue, a scheme was developed to modify sulfated CNCs with 3-aminopropyl-triethoxy silane (APTES). The functionalization was confirmed with thermal gravimetric analysis, Fourier transform infrared spectroscopy, dynamic light scattering, elemental analysis, and energy dispersive spectroscopy (EDS). Studies of reaction stoichiometry and conditions showed that a 5% degree of substitution could be achieved without promoting significant aggregation. Tensile testing and nanoindentation studies of shear cast films showed no significant differences in the tensile strength and Young’s moduli of films produced from the modified and unmodified CNC. However, APTES-CNC films had significantly more hydrolytic stability than unmodified CNC based on dissolution in water and mass loss studies. These results suggest that CNC-APTES modification can be promising for enhancing hydrolytic stability without compromising the inherent mechanical properties of CNCs.