ABSTRACT
Cellulose is the most abundant renewable polymer on earth. It is a linear polysaccharide with long chains, which consists of β-d-glucopyranose units joined by β-1,4-glycosidic linkages (Figure 5.1). Due to the absence of side chains or branching, cellulose chains can exist in an ordered structure. It results in the semicrystalline structure of cellulose, with both crystalline and amorphous regions. The hydrogen bonding between the cellulose chains and van der Waals forces between the glucose units give rise to crystalline regions in cellulose.1 Cellulose is bestowed with many attractive physical and chemical properties like biocompatibility, biodegradability, hydrophilicity, stereoregularity, presence of reactive hydroxyl groups, and ability to form suprastructures.2,3
The main sources of cellulose are wood, cotton, and aerobic bacteria. However, the most important source of commercial cellulose is wood pulp.3 The cellulose content of cotton ber is 90% and that of wood is 40%–50%. Most wood pulp is utilized in making paper and cardboard. Cellulose derivatives, mainly esters and ethers, like ethyl cellulose, hydroxyethyl cellulose, hydroxyl propyl cellulose, methyl cellulose, carboxymethyl cellulose, and cyanoethyl cellulose4-10 have been synthesized and found applications as bers, lms, coatings, laminates, optical lms, and sorption media, as well as additives in building materials, pharmaceuticals, foodstuffs, and cosmetics. The scope of utility of cellulose could be further enlarged by its modication by graft copolymerization.
