Chemical Functionalization of Cellulose Nanofibrils with 2-Aminoethyl Hydrogen Sulfate

The chemical functionalization of cellulose nanofibrils (CNFs) was carried out using 2-aminoethyl hydrogen sulfate as the reagent under various experimental conditions via a bimolecular nucleophilic substitution (S_N2) reaction. The functionalized CNFs were characterized by Fourier transform infrared spectroscopy-attenuated total reflectance. The results indicate that the chemical modification was successful, as evidenced by the presence of a band at 1540 cm^-1, corresponding to the N-H bond of the amine group. Elemental analysis revealed a nitrogen content of 0.45%, and the degree of substitution was calculated to be 0.053 under the optimal reaction conditions. Atomic force microscopy analysis showed no significant changes in the morphology of the CNFs. X-ray diffraction patterns demonstrated a decrease in the crystallinity index, from 80.8% to 71.8%. Thermogravimetric analysis showed a slight reduction in thermal stability (onset temperature decreased from 229.4 to 227.5 °C) for the modified CNFs compared to the unmodified samples. Differential scanning calorimetry results indicated no significant effect of the modification on thermal behavior, with both modified and unmodified samples displaying similar thermal profiles, although the modified samples exhibited slightly higher thermal stability.