Constructing reactive “rod-bead” nanohybrid-driven high-efficient crosslinking network for the preparation of strong and tough plant protein adhesive

There still exist challenges to regulate the crosslinking network of soybean flour (SF) precisely with both strong and tough mechanical properties to match adhesion requirements of wood adhesives applications. Herein, a novel nanohybrid crosslinker with dynamic bonding effect was synthesized and then employed to improve SF adhesives. Dimethylglyoxime as chain extender was incorporated into polyurethane cooperating with CuO to form dynamic coordination bonds, after which epoxy and siloxane dual-functionalized polyurethane was co-deposited onto cellulose nanocrystal (CNC) surface to construct reactive “rod-bead” nanohybrid named CuOGU@CNC. It is found that epoxy groups induce CuOGU@CNC to form covalent crosslinking interactions with SF matrix constructing a stable adhesive system. Meanwhile, the dynamic coordination bonds of dimethylglyoxime and CuO serve as sacrificial units to contribute for energy dissipation, during which the unique “rod-bead” structure increases contact efficiency between DMG and CuO to optimize bonding exchange rate to high-effectively redistribute stress during loading. Given on the effect, the adhesives modified by CuOGU@CNC present improved dry and wet adhesion strength, and adhesion toughness compared to pristine SF sample. This work can provide a facile strategy to prepare high-performance wood adhesives aiming to meet higher applicational standard.