Natural monomers: A mine for functional and sustainable materials – Occurrence, chemical modification and polymerization

Owing to the natural abundance, variety of structural features, and highly specific functions, natural monomers render themselves as potential candidates for production of high performance functional polymers. The emerging concept of the biorefinery and development of new biosynthetic routes to synthesize a versatile and broad spectrum of natural monomers and polymers continues to gain momentum. The production of high quality polymers from renewable feedstocks requires innovative chemical modifications and catalytic transformations to achieve higher yields in an efficient manner. A fresh look into monomers available from natural resources such as terpenes, rosin, glycerol, furans, tannins, suberin, their derivatives and miscellaneous monomers may inspire future applications with impactful biobased materials. There are also many areas that require urgent discussion and review pertaining to recent developments in the field; this includes monomer sources that give molecules having special structural features. In particular, cardanol, a naturally occurring low-molecular-weight compound is unique as it contains a phenolic head group and a hydrocarbon chain with different degrees of unsaturation. This molecule possesses functional groups that are amenable for classical chemical modification, which is instrumental in developing a wide range of functional monomers and polymers. A large number of soft and hard materials have been developed from cardanol-based monomers. During the past, a large number of industrial grade materials have been developed from plant-based monomers, including development from microbial and fermentation processes (i.e. lactic acid). This review provides a comprehensive study and survey on recent developments on monomers and polymers derived from urushiol and cardanol based monomers and polymers, vegetable oil-based monomers and polymers, microbially produced monomers and polymers. These all represent emerging fronts giving a vast scope while highlighting important potential material and reagent opportunities.