Hydroxyl Changing Mechanism of Cotton Cellulose during Alkaline Treatment Characterized by ATR-FTIR in Combination with Two-Dimensional Correlation Spectroscopy

Hydroxyl changes of cotton cellulose treated with sodium hydroxide (NaOH) solution is closely related with hydrogen bonding (H-bonds) between different hydroxyls, which is difficult directly measure by common instrumentational methods of X-ray diffraction (XRD) or Fourier transform inf. red FIR) spectroscopy. Two-dimensional correlation spectroscopy (2Dcos) is a powerful tool to analy T the changes . 4 molecular spectroscopy. In this study, the alkalinetreated cotton cellulose was monitored in real tinie by attenuated total reflection (ATR) in combination with 2Dcos. Results indicated that the H-bonds changed in the following sequence order: nu(O3-H3 center dot center dot center dot O5) (intramolecular) -> nu(O6-H6 center dot center dot center dot O3') (intermolecular) -> nu(O2-H2 center dot center dot center dot O6) (intramolecular). Moreover, Gaussian computational modeling analysis also confirmed this mechanism. Both XRD and FTIR results indicated the decrease of crystallinity of the alkaline -treated cotton cellulose over prolonged time.