Bioinspired catechol-based sizing agents featuring substrate-independent adhesion and vinyl reactivity for synergistically reinforced carbon fiber/vinyl ester composites

The interfacial properties of carbon fiber-reinforced vinyl ester resin (CF/VE) composites are critical for their performance in extreme environments. Inspired by mussel adhesive chemistry, a series of polyethylene glycol-modified epoxy (EPE)-based sizing agents were designed with controlled catechol functionalities and vinyl grafting ratios. The optimized formulation, 0.15Vi/0.2Mu, contained catechol and vinyl groups occupying 20% and 15% of EPE hydroxyl sites, respectively. AFM force-distance measurements using sizing agent-modified probes showed a catechol content-dependent increase in adhesion force, confirming the substrate-independent adhesive capability of catechol moieties on the carbon fiber surface. Meanwhile, vinyl groups copolymerized with the VE matrix during curing, forming covalent crosslinks. Owing to the synergistic effects of catechol-mediated adhesion and vinyl-induced copolymerization, 0.15Vi/0.2Mu-CF/VE composites exhibited significantly improved interfacial performance. The interlaminar shear strength, interfacial shear strength, and fracture toughness reached 69.25 MPa, 66.94 MPa, and 78.35 J/m 2 , representing increases of 35.0%, 107.6%, and 371.4%, respectively, compared with untreated D-CF/VE composites. This work provides an effective strategy for interfacial engineering of high-performance VE-based composites.