Swelling and Dissolution of Cellulose

When bone-dry cellulose fibers are exposed to humidity, they adsorb water and the cross section of the fibers is increased because of swelling. At a 100% relative humidity this swelling corresponds roughly to a 25% increase in the fiber diameter. An additional 25% increase in swelling takes 

The water retention of cellulose fibers at a given relative humidity varies depending on whether the equilibration has taken place by desorption or adsorption. (hysteresis). The water uptake also continuously decreases after repeated drying and moistening of the fibers. Additional factors influencing the ability of pulp fibers to swell are their chemical composition, such as their hemicellulose and lignin content. 

Cellulose swells in electrolyte solutions because of the penetration of hydrated ions which require more space than the water molecules. 

The ability of inorganic salt solutions to swell and even dissolve cellulose is usually related to the lyotropic series for the solvated ions but the mechanism is complicated. 

Alkali is not capable of dissolving native cellulose. Only depolymerized cellulose fragments with a low degree of polymerization are alkali soluble. Certain quaternary ammonium compounds are more effective resulting in full solubility, A mixture of dimethyl sulfoxide and paraformaldehyde (DMSO-PF) has interesting properties as a cellulose solvent. However, its effect depends at least partly on the formation of a hydroxymethylcellulose derivative. The most important cellulose solvents are metal complexes of 

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