The behavior of cellulose molecules in aqueous environments

Molecular motions of cellulose chains in aqueous environments were investigated by comparison with those in non-aqueous environments using molecular simulation techniques. The cellulose chains under nonaqueous conditions approached each other closely and then made tight aggregates that were formed by direct hydrogen bonding. Those in aqueous environments, such as in a bio-system, were separated from each other by water molecules and did not have direct hydrogen bonding between the cellulose chain molecules. Folded-chain structures were not found in either aqueous or non-aqueous environments that were somewhat crowded. In the aqueous system, the water molecules around the cellulose chains restricted their molecular motions and interrupted formation of direct, interchain hydrogen bonds. In the non-aqueous system, the cellulose chains approached each other closely and then made a tight cluster before the chain molecules could wind and bend. It was concluded that a very dilute solution of cellulose molecules in appropriate solvents is necessary to create folded-chain or random-coiled structures. We also confirmed that the driving force for making tight clusters of cellulose molecules in highly concentrated solutions is the energy of the hydrogen bonding created directly between the hydroxyl groups of the cellulose chains. These results strongly suggest that hydrogen bonding plays a very important role in the characteristics of cellulose molecules.