Construction of interfacial dynamic bonds for high performance lignin/polymer biocomposites

Lignin is the largest natural aromatic biopolymer,but usually treated as industrial biomass waste.The development of lignin/polymer biocomposites can promote the high value utilization of lignin and the greening of polymers.However,the weak interfacial interaction between industrial lignin and polymer induces poor compatibility and serious agglomeration in polymer owing to the strong intermolecular force of lignin.As such,it is extremely difficult to prepare high performance lignin/polymer biocomposites.Recently,we proposed the strategy of in situ construction of interfacial dynamic bonds in lignin/polymer composites.By taking advantage of the abundant oxygen-containing polar groups of lignin,we inserted dynamic bonding connection such as hydrogen bonds and coordination bonds into the interphase between lignin and the polymer matrix to improve the interfacial interactions.Meanwhile,the natural amphiphilic structure characteristics of lignin were utilized to construct the hierarchical nanophase separation structure in lignin/polymer composites.The persistent problems of poor dispersity and interfacial compatibility of lignin in the polymer matrix were effectively solved.The lignin-modified polymer composites achieved simultaneously enhanced strength and toughness.This concise review systematically summarized the recent research progress of our group toward building high-performance lignin/polymer biocomposites through the design of interfacial dynamic bonds(hydrogen bonds,coordination bonds,and dynamic covalent bonds)between lignin and different polymer systems(polar plastics,rubber,polyurethane,hydrogels,and other polymers).Finally,the future development direction,main challenges,and potential solutions of lignin application in polymers were presented.