title: Temperature-dependent structural changes in hydrogen bonds in microcrystalline cellulose studied by infrared and near-infrared spectroscopy with perturbation-correlation moving-window two-dimensional correlation analysis.
abstract: Temperature-dependent structural changes in hydrogen bonds (H-bonds) in microcrystalline cellulose (MCC) were investigated by infrared (IR) and near-infrared (NIR) spectroscopy. The O-H stretching fundamentals and their first overtone bands were employed to explore the structural changes. In order to analyze the overlapping OH bands due to various H-bonds, perturbation-correlation moving-window two-dimensional (PCMW2D) correlation spectroscopy was applied to the IR and NIR data. Typical spectral variation temperatures were visualized by the PCMW2D correlation analysis. Structural changes in the strong H-bonds in MCC gradually occur in the temperature region of 25-130 degrees C, and they become greater above 130 degrees C. Both OH groups with H-bonds of intermediate strength and very weak H-bonds arise from the structural change of strong H-bonds in the temperature region of 40-90 degrees C, whereas the appearance of the latter OH groups with very weak H-bonds gradually becomes dominant above 90 degrees C. It is revealed from the present study that the glass transition at 184 degrees C induces the changes in the H-bonds in the Ibeta and the O3-H3...O5 intrachain H-bonds. Band assignments for the O-H stretching first overtone vibration region are proposed based on the results of the PCMW2D correlation analyses.
authors.affiliation: Department of Chemistry and Research Center for Near Infrared Spectroscopy, School of Science and Technology, Kwansei Gakuin University, 2-1 Gakuen, Sanda 669-1337, Japan.
authors.forename: Akihiko
authors.initials: A
authors.lastname: Watanabe
authors.forename: Shigeaki
authors.initials: S
authors.lastname: Morita
authors.forename: Yukihiro
authors.initials: Y
authors.lastname: Ozaki
mesh_terms: D000465:Algorithms; D002482:Cellulose / Q000737:chemistry* / Q000648:ultrastructure; D003461:Crystallography / Q000379:methods*; D003627:Data Interpretation, Statistical; D006860:Hydrogen Bonding; D008968:Molecular Conformation; D013055:Spectrophotometry, Infrared / Q000379:methods*; D013223:Statistics as Topic; D013696:Temperature
chemical_list: D002482:Cellulose; C109691:microcrystalline cellulose