Coupling chitosan and TEMPO-oxidized nanofibrilliated cellulose by electrostatic attraction and chemical reaction

This study reports coupling methods of chitosan (CTS) and TEMPO-oxidized nanofibrilliated cellulose (TONCs). Coupling chitosan, a cationic polysaccharide, to anionic TONCs is preformed through physical crosslinking via ionic bond formation at room temperature and carefully controlled pH and mass ratio. After heating, the carboxyl group of TONCs and the ammonium group of chitosan react into an amide covalent bond linkage-CONH-. Fourier Transform infrared spectroscopy, C-13 solid-state nuclear magnetic resonance, are used to confirm the bonds. Films of the modified TONC are produced by casting and exchanging method and atomic force microscopy and thermogravimetric analysis was used to study the film properties. Further, the tensile strength of the CTS-TONCs films is improved for the covalent bond produced indicating a straight forward method to augment the properties of these all-polysaccharide films.