Seed-Germination-Inspired Robust Protein-Based Bioadhesives Made by Regulating Dynamic Water

Soybean-meal adhesives offer a renewable alternative to fossil-derived formaldehyde resins for wood composites, but their bonding performance is highly sensitive to water availability during processing. Water promotes protein-chain mobility, wetting, and penetration into porous wood, whereas premature water loss during open assembly restricts molecular rearrangement, causes rapid thickening, and weakens interfacial development. Inspired by water regulation during seed germination, we constructed a temperature-sensitive poly(amidoamine)–glutaraldehyde network in a soybean-meal adhesive to regulate water loss and flow during processing. Before hot pressing, hydrogen bonding and network confinement reduced premature water loss; upon heating, weakened hydrogen-bonding interactions and network rearrangement reduced the confinement of associated water, thereby preserving adhesive flow and promoting interfacial penetration. After 2 h of open assembly, the modified adhesive retained 46% more water than the unmodified soybean-meal adhesive and 14% more than a PAE-modified soybean-meal adhesive. Subsequent hot pressing produced plywood with a wet shear strength of 0.71 MPa, 1320% and 78% higher than the respective controls. Under standard processing conditions, wet shear strength reached 1.39 MPa, representing increases of 184% and 34%. Comparative life-cycle assessment further indicated lower potential environmental impacts than conventional urea-formaldehyde and phenol-formaldehyde resins within the assessed system boundary.