ABSTRACT
Figure 7.1 Glucopyranosic units of cellulose.Macromolecules of natural cellulose various origins may include 2000 to 30,000 elementary units. During process of cellulose isolation from plant materials and cellulose modification, a partial depolymerization of the macromolecules is observed.Each glucopyranosic unit of cellulose contains three hydroxyl functional groups: one primary and two secondary groups. The hydroxyl groups impart to cellulose materials an increased hydrophilicity and sorption. Besides, owing to hydroxyl groups, cellulose can form ethers and esters, carbonyl, carboxyl, and other derivatives. Due to presence in cellulose chains of labile glucosidic (semi-acetal) chemical bonds, this polysaccharide is depolymerized under effect of oxidants, acids and cellulolytic enzymes, mainly in non-crystalline domains (Fengel, 1984).
