Synthesis of advanced biobased green materials from renewable biopolymers

Polymeric materials such as hydrogels have become necessary in our daily lives. Hydrogels are three-dimensionally cross-linked polymeric networks that can absorb large amounts of water. Thanks to their properties, hydrogels are very useful in multiple application fields. However, they have usually been obtained from petroleum-derived polymers, contributing to plastic pollution and global warming. In this context, biomass has emerged as an appropriate alternative for the production of chemicals, building blocks and biopolymers. Lignin is the second most ample and disposable biopolymer in the world. This biopolymer has been underutilised until recent decades, but as it has demonstrated to provide composite materials such as hydrogels with excellent features, its valorization would mean a step forward in sustainability and circular economy. Hence, this review focuses on the state-of-art of hydrogels and lignin-hydrogels, as well as on their current applications.