Chemical Structures of Cellulose, Hemicelluloses, and Lignin

Solid state structures of cellulose, that is, intra- and intermolecular hydrogen bonds, crystallinity, crystal size, crystal structures, interactions with water, molecular mass and molecular mass distributions, presence of lignin or hemicelluloses, shape and size of cellulosic materials and others, greatly influence reactivity of the cellulosic materials, efficiency of the reactions, and finally properties of the chemically modified cellulosic materials. Although structures and distributions of hemicelluloses have been comprehensively studied in the last 20 years, their physiologic meanings in a cell wall are not known yet. Lignins are classified into several types according to their composition of structural units. Structural heterogeneity of lignin in various topochemical regions of wood must be considered for total understanding of lignin. Lignin structurally specific to the type of a cell and to the stage of cell maturation is deposited in the cell wall regardless of the structural types of the precursors adminstered.