Fabrication of Lignin Based Renewable Dynamic Networks and Its Applications as Self-healing, Antifungal and Conductive Adhesives

Abstract The preparation of dynamic networks from lignin with multipurpose and multifunctional practical applications is highly desirable but still challenging. In this study, the combination of a “grafting from” reversible addition-fragmentation chain transfer (RAFT) polymerization and dynamic chemistry was utilized to synthesize lignin based dynamic networks. Vanillin, a derived chemical from lignin, was used as a building block to realize the structural reorganization of lignin via RAFT polymerization, together with fatty acid derivative as the comonomer. NMR analysis confirmed the expected structures. It was demonstrated that the physicochemical properties of grafted lignin were adjustable depending on polymerization reaction conditions. Due to the presence of aldehyde groups from vanillin moiety, a dynamic network was produced by using diamines as crosslinkers. The mechanical properties were also tunable via controlling the structure of crosslinkers. The crosslinked lignin-based dynamic networks exhibited various interesting properties, such as recyclability and UV-adsorption ability. In addition, it could be used as self-healing, antifungal and conductive adhesives. The shear strength after first time self-healing could reach 2.9 MPa, which was 83.1% of the pristine adhesion. This damage and repair process could be carried out at least four times under relatively low temperature (80 °C) and pressure (1.0 MPa). More importantly, antifungal activity was observed for the self-healing adhesive, which might enlarge its applications. Additionally, after the addition of carbon nanotubes, the generated conductive adhesive was weldable without compromising its conductivity. This study has demonstrated the potential of lignin to synthesize high value-added materials, which could be appealing to both biorefinery and materials society.