From plant phenols to novel bio-based polymers

Replacing petroleum-based products with inexpensive, biorenewable, natural materials is important for sustainable development and will have a significant impact on the polymer industry and the environment. Biorenewable aliphatic and cycloaliphatic compounds are less competitive with counterparts with aromatic structures for advanced polymeric materials in terms of rigidity, hydrophobicity, as well as chemical and thermal stability. Biorenewable plant phenols represent a diverse class of chemicals with a great industrial significance due to their unique structures and high abundance. The depolymerization process of lignin into small bio-based phenols is a relatively new approach and has received a considerable attention recently. This process produces key intermediates, phenolic compounds that can be used to develop and design wide range of high performance biorenewable multifunctional polymers and composites. In this review article, the production of biorenewable phenols from natural sources such as lignin by energy-, catalytic-, enzymatic-assisted depolymerization processes will be summarized. The different chemical modifications and polymerization pathways to obtain bio-based polymers (e.g. vinyl ester resins, cyanate ester, epoxy, benzoxazine resins, etc.) will be discussed. In addition, this review article will conclude with an overview of current and potential future applications of the bio-sourced phenolic-based materials in a wide range of automotive, electrical, and medical applications. Overall, the present review article will provide a quantitative experimental basis for the depolymerization process of lignin to produce biorenewable multifunctional phenolic-based polymers to increase our level of understanding of the behavior of this important class of polymeric materials and other similar bio-based polymers.