Aldehyde-functionalization of chitin nanocrystals via SI-ARGET ATRP of lignin-derived monomers

Chitin nanocrystals (ChNCs), prepared from a down-sizing process from chitin, have recently captured great attention to access sustainable nanomaterials. The surface modification of ChNCs is crucial to regulate the surface physicochemical properties and introduce specific functions, thus satisfying their diverse applications. In this study, aldehyde-functionalized ChNCs (ChNCs-PVMA) with enhanced hydrophobicity were developed via surface-initiated activators regenerated by electron transfer for atom transfer radical polymerization (SI-ARGET ATRP) of a lignin-derived polymerizable aldehyde monomer, vanillin methacrylate (VMA). The monomer conversion was determined by ¹H NMR spectroscopy of the reaction mixture based on the change of the relative ratio of VMA and solvent signals. The prepared ChNCs-PVMA were systematically characterized by FTIR, CP/MAS ¹³C NMR, XPS, XRD, DSC, TGA, and TEM. The dispersibility of ChNCs and ChNCs-PVMA in water and DMF was evaluated by dynamic light scattering and visual observation, indicating good dispersion of ChNCs-PVMA in organic solvents. Furthermore, based on the available aldehyde groups, the ChNCs-PVMA was reacted with amino acids via Schiff base reaction, demonstrating a rich follow-up chemistry towards diverse functions by the reactive aldehyde groups.