The interaction of water with cellulose stages many unresolved questions. Here2H MAS NMR and IR spectra recorded under carefully selected conditions in1H-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 the1HO(2) and1HO(6) hydroxyl groups of the constituting glucose units act as hydrogen-bond donors to water, while the1HO(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.
- H MAS NMR
- Deuterium exchange
- Hydroxyl groups
- Molecular-dynamics simulation