Molecular manipulation of lignin by phytogenic protein to enable its multifunctionality for water resistance and anti-mildew adhesive

Wood products are widely used in furniture and building materials, but the adhesives used to bond wood components are mainly formaldehyde-based resins, which are toxic, and most of their raw materials come from non-renewable resources. Replacing aldehyde-based adhesives with renewable materials is challenging for the development of wood-based panels. Here, we designed an aldehyde-free multifunctional adhesive with a rigid structure based on lignin and phytogenic protein. To enhance the defects of current phytogenic protein adhesives, as their poor water resistance and vulnerability to microbial erosion, this paper used phytogenic protein to regulate lignin and synthesized a triblock copolymer of three kinds of agricultural and forestry wastes, including lignin, camellia meal, and soybean meal, and finally made it form a densely cross-linked structure. This covalent crosslinking and block copolymerization strategy endowed the adhesive with a bonding strength of 1.03 MPa, which is comparable to that of commercial adhesives. It also showed good inherent mildew resistance, and its performance was better than previously reported adhesives that used chemical preservatives. This efficient, environmentally friendly, and low-cost design strategy can be used to convert low-cost natural biomass resources into high-value green products to alleviate environmental pollution and energy concerns associated with the use of petroleum-based materials. • Triblock copolymer was synthesized from three kinds of agricultural and forestry wastes. • Lignin was regulated by phytogenic protein to increase its activity effectively. • The water-resistant bonding strength of the aldehyde-free adhesive was increased by 77.7%. • The biomass adhesive has good self-mildew resistance.