Designing Biomimetic Microphase-Separated Motifs to Construct Mechanically Robust Plant Protein Resin with Improved Water-Resistant Performance

Plant protein, as a sustainable alternative to petroleum-derived resin, has exhibited notable potential for engineering wood products without formaldehyde emission, while the poor mechanical and water-resistant performances limit its practical applications. Inspired by mussel chemistry and structure, a dopamine-functionalized polyurethane (D-PU) elastomer is synthesized in this work acting as a bio-inspired crosslinking unit to improve the properties of soy protein (SP) resin. It is found that the catechol groups of the incorporated D-PU not only triggers polyurethane to interact with SP matrix giving rise to a stable crosslinking network with excellent load-bearing capacity, but also serves as a water-resistant barrier to reduce the water erosion effect on resin. Moreover, a desired microphase-separated morphology is observed within the continuous protein phase after introducing D-PU. The microphase-separated structure simultaneously strengthens and toughens SP adhesive layer, thus achieving high-efficiency stress transfer and energy dissipation as well as accelerating SP to further permeate into the substrate forming more mechanical adhesion nails. As a result, the modified SP-D-PU resin presents an impressive improvement in dry and wet adhesion strength up to 70.5% and 133.9% compared to the pristine SP resin, respectively. The proposed biomimetic design may offer a workable strategy for preparing of high-performance bio-based composites.