Enhanced strength and toughness of epoxy resin through a controllable cross-linked network with a rigid-flexible interchain structure

Oxide nanomaterials are widely used to enhance the mechanical properties of epoxy resins (EP) owing to their high strength and toughness. However, the stress concentration caused by agglomeration limits their performance. This paper proposes a new method to simultaneously improve the strength and toughness of EP by introducing CuO nanorods with a surface-grafted flexible linear polymer into the EP cross-linking network. This forms a rigid–flexible chain interpenetrating structure in the system, and covalent bonding with the EP network, facilitating the controllable adjustment of the crosslinking density of the system. Thus, the goal of simultaneously enhancing and toughening the EP is achieved. Experimental results show that the strength and toughness of modified BCN-CuO/EP are 91.2 and 1.77 MPa·m^1/2, respectively, which are 76.0% and 92.3% better than those of pure EP, respectively. This study provides new insights for improving the mechanical performance of EP. Highlights: The integration of CuO nanorods with flexible linear polymers (BTCI) led to a 76.0% increase in strength and a 92.3% improvement in toughness of the epoxy resin (EP), showcasing significant performance gains. The study introduced a novel “rigid–flexible” chain interpenetrating network in EP, achieved through covalent bonding, which optimally adjusts crosslinking density and mitigates stress concentration. The research highlights the effectiveness of combining CuO nanorods with BTCI in EP systems, opening new pathways for enhancing the mechanical characteristics of composite materials.