Chemical modifications of lignin

Lignin constitutes one of the three major components of lignocellulosics (15%−30% by weight, 40% by energy). Lignin is a natural amorphous biopolymer that acts as the essential glue, providing structural integrity to the plan cell wall and consequently the plant itself. Lignin is defined as a random, amorphous, three-dimensional polymeric network that does not possess a uniform, homogeneous, and well-defined structure with well-established repeating units. Lignin is mainly composed of aromatic phenylpropenyl units randomly branched. The availability of lignin and its versatile native structure suggests that it could play a central role as chemical feedstock, particularly in the formation aromatic chemicals and polymeric materials. Lignin-based polymeric materials were prepared for primarily applications, such as dispersants, emulsifiers, binders, adhesives, and fillers. However, nowadays novel lignin-based materials are being designed through various and sophisticated chemistries to lead materials for high demanding applications ranging from coating, biomedical, composites, etc. The present chapter collates recent advances in the chemical modifications of lignin and/or lignin-derived building blocks to form functional polymer materials.