Reactivity and Accessibility of Cellulose, Hemicelluloses, and Lignins

Since the modification of wood polymers is generally conducted in a heterogeneous system, the apparent reactivity would be influenced by both the chemical and the physical nature of the substrate as well as of the reactant molecules involved. The significance of the accessibility factor in affecting the reactivity of cellulose has been well recognized and is generally related to crystallinity of the substrate. However, the reactivity of cellulose cannot be explained entirely by its apparent crystallinity. It is also profoundly influenced by its supramolecular structure. The accessibility factor also plays a role in certain reactions of the hemicellulose and lignin components, although these polymers appear to be amorphous when present in the plant tissues. This chapter discusses major factors affecting the reactivity of cellulose, hemicelluloses, and lignin under both acidic and alkaline modifications. Accessibility plays a dominant role in the oxidative degration of cellulose.