Effects of Hydrophilic and Hydrophobic Solvents on Solid Structure and Molecular Mobility of Cellulose

Crystalline cellulose was ball-milled in the presence of a hydrophilic or low polarity solvent, and the changes in the solid structure caused by interaction with the solvent were analyzed by NMR relaxation time and thermally stimulated depolarization current (TSDC) method. The cellulose particles were prepared by ball-milling with obviously different morphology and crystallinity depending on the nature of solvents. The molecular mobility of cellulose chain was enhanced by the interaction of hydrophilic solvents compared with the interactions of low polarity solvents. The TSDC analyses of the cellulose with different morphology and crystallinity confirm the existence of α, β and γ relaxations. The intensities of α and β relaxations increased with decreasing in crystallinity of the cellulose, accompanied with a shift of the peak temperature to lower values. The γ relaxation was proved to be independent from other two relaxations. The presence of water in the cellulose gave higher intensity of α and β relaxations, while the presence of toluene mainly affected the intensity and peak temperature of the β relaxation. The study on local relaxation modes of solid cellulose revealed the specific interaction of cellulose chains and solvents molecule, depending on the solvent charateristics.