Exploring structural variations of hydrogen-bonding patterns in cellulose during mechanical pulp refining of tobacco stems.

Hydrogen bonding and mechanical refining are closely correlated. In this work, structural variations of hydrogen bonding patterns in cellulose during mechanical pulp refining, including the hydrogen bonding energy and distance as well as the content of hydrogen bonds, have been explored by using the second derivative FTIR spectra and deconvolving spectra in the OH stretching vibrational region. Results show that except for the bond distance, both the hydrogen bonding energy and the content of hydrogen bonds exhibit a significant variation at an increasing beating degree. The calculated hydrogen bonding energies for intermolecular O6H⋯O3' decrease by 12.9%, while those of intramolecular O3H⋯O5 and O2H⋯O6 vary little. Evolutions of the content of certain hydrogen bonds differ depending on the different refining stage. It is suggested that along with the role of water, hydration and swelling, internal/external fibrillation and delamination are strongly related to the structural variations of hydrogen bonding patterns in cellulose during mechanical pulp refining.