ABSTRACT

The possible locations of water molecules in cotton fibers are explored based on fiber size, crystallite size, known crystal structures of cellulose hydrates, and cross-sections of swollen cotton fibers. A 5% moisture content, a normal value for room conditions, corresponds to roughly 760 monolayers of water if it all goes on the external fiber surface, or about 0.3 monolayers if it were able to access all surfaces of the crystallites that are indicated by x-ray diffraction studies. Additional information on hydrogen bonding, the major mechanism for the interaction of water and cotton, is provided by studies of water clusters with quantum mechanics. These theoretical studies show variation on the order of 10% in the length of hydrogen bonds, depending on the position of the water relative to other water molecules. These poorly understood fine distinctions are not found with studies based on available empirical force fields, the only method fast enough to be used for production studies on large molecules such as cellulose, so the empirical methods must be modified appropriately.