Sericin-Inspired Multilevel Supramolecular Networks Enable Strong and Cold-Pressable Gelatin-Based Wood Adhesives

This study aims to address the challenge of developing formaldehyde-free wood adhesives with high strength, high toughness, and low-temperature processability. Inspired by the cooperative organization of sericin, a Gel/LA/TA bio-based adhesive was designed by integrating gelatin (Gel) as a continuous protein scaffold with α-lipoic acid (LA) and tannic acid (TA) to construct a multicomponent supramolecular network. Multiscale analyses revealed that LA and TA altered the molecular environment of gelatin, disrupted LA crystallinity, restricted molecular mobility, and promoted the formation of a dense supramolecular network dominated by hydrogen bonding and other noncovalent interactions. After 24 h postpress conditioning at room temperature, Gel/LA/TA-bonded plywood exhibited shear strengths of 2.7 MPa and 3.6 MPa for specimens pressed at 25 °C and 120 °C, respectively. Its delamination work reached 2591.21 N·m–1, representing a 474.2% increase over gelatin. The wood fiber pull-out and bridging at the fracture surface, along with a wood destruction rate of approximately 90%, demonstrated enhanced interfacial load transfer capability. Comparison with the control group containing octanoic acid indicates that the disulfide-containing structure of LA contributed additional reinforcement to the adhesive network. The Gel/LA/TA adhesive also exhibited thermally assisted self-healing behavior and adhesion to multiple substrates, and outperformed conventional phenolic resins in most environmental impact indicators in a life cycle assessment. This study provides a supramolecular design practical strategy for developing high-performance, low temperature processable, and environmentally friendly gelatin-based wood adhesives.