Non-exchanging hydroxyl groups on the surface of cellulose fibrils: The role of interaction with water

• Published in: Carbohydrate research 2016-11, Vol.434, p.136-142
• Main Authors: Lindh, Erik L., Bergenstråhle-Wohlert, Malin, Terenzi, Camilla, Salmén, Lennart, Furó, István
• Format: Article
• Language: English
• Subjects: 2H MAS NMR; Cellulose; Cellulose - chemistry; Deuterium exchange; FT-IR; H MAS NMR; Hydrogen Bonding; Hydroxyl groups; Magnetic Resonance Spectroscopy; Molecular Dynamics Simulation; Spectrophotometry, Infrared; Water - chemistry
• ISSN: 0008-6215; 1873-426X; 1873-426X
• DOI: 10.1016/j.carres.2016.09.006

The interaction of water with cellulose stages many unresolved questions. Here 2H MAS NMR and IR spectra recorded under carefully selected conditions in 1H-2H exchanged, and re-exchanged, cellulose samples are presented. It is shown here, by a quantitative and robust approach, that only two of the three available hydroxyl groups on the surface of cellulose fibrils are exchanging their hydrogen with the surrounding water molecules. This finding is additionally verified and explained by MD simulations which demonstrate that the 1HO(2) and 1HO(6) hydroxyl groups of the constituting glucose units act as hydrogen-bond donors to water, while the 1HO(3) groups behave exclusively as hydrogen-bond acceptors from water and donate hydrogen to their intra-chain neighbors O(5). We conclude that such a behavior makes the latter hydroxyl group unreactive to hydrogen exchange with water. [Display omitted] •Cellulose-water interaction was examined by 2H MAS NMR and FTIR using hydrogen-deuterium exchange.•Only two of the three available hydroxyl groups on cellulose are exchanging their hydrogen.•MD simulations confirm that only the HO(2) and HO(6) hydroxyl groups act as hydrogen bond donors.