John J. Meister

Review of the Synthesis, Characterization, and Testing of Graft Copolymers of Lignin

Lignin [8068-00-6] is a natural product produced by all woody plants. It is second only to cellulose in mass of polymer formed per annum.1 Lignin constitutes between 15 and 40 percent of the dry weight of wood with variation in lignin content being caused by growing conditions, species type, the parts of the plant tested, and numerous other factors2. Plants use lignin to 1. control fluid flow, 2. add strength, and 3. protect against attack by microorganisms3.Each cell of the plant grows its own lignin. The cell undergoes “lignification” in response to an internally-orchestrated series of reactions which take place all during cell differentiation3. Lignin appears first in the primary (exterior) wall of the cell “corners”. As the cell grows, lignin deposits throughout the primary wall and then appears in the secondary, interior wall of the cell. During this growth period, lignin deposits develop in the intercellular region, also. Lignin appears to be attached to the crystalline microfibrils of cellulose by phenylpropane linkages to carboxyl groups. Such a bond structure would be a uronic acid ester linkage.3