Chemical Functionalization\nof Cellulose Nanofibrils\nwith 2‑Aminoethyl Hydrogen Sulfate

The chemical functionalization of cellulose nanofibrils\n(CNFs)\nwas carried out using 2-aminoethyl hydrogen sulfate as the reagent\nunder various experimental conditions via a bimolecular nucleophilic\nsubstitution (S<sub>N</sub>2) reaction. The functionalized CNFs were\ncharacterized by Fourier transform infrared spectroscopy-attenuated\ntotal reflectance. The results indicate that the chemical modification\nwas successful, as evidenced by the presence of a band at 1540 cm<sup>–1</sup>, corresponding to the N–H bond of the amine\ngroup. Elemental analysis revealed a nitrogen content of 0.45%, and\nthe degree of substitution was calculated to be 0.053 under the optimal\nreaction conditions. Atomic force microscopy analysis showed no significant\nchanges in the morphology of the CNFs. X-ray diffraction patterns\ndemonstrated a decrease in the crystallinity index, from 80.8% to\n71.8%. Thermogravimetric analysis showed a slight reduction in thermal\nstability (onset temperature decreased from 229.4 to 227.5 °C)\nfor the modified CNFs compared to the unmodified samples. Differential\nscanning calorimetry results indicated no significant effect of the\nmodification on thermal behavior, with both modified and unmodified\nsamples displaying similar thermal profiles, although the modified\nsamples exhibited slightly higher thermal stability.