Functionalized Copolymer‐Mediated Interfacial Optimization in Carbon Fiber‐Reinforced Epoxy Composites

To meet green manufacturing requirements and further enhance interfacial crosslinking density, an environmentally friendly ethanol/water mixed solvent system was used. Using RAFT polymerization, this system synthesized an eco‐friendly copolymer sizing agent (PAE) with high hydrophilicity and high reactivity. The main chain of PAE is rich in hydroxyl side chains and incorporates terminal carboxyl groups. CF‐PAE‐1, obtained through impregnation treatment, successfully constructed a bidirectional chemical “stitching” network on the fiber surface. Its surface energy significantly increased to 60.58 mJ/m 2 , and the polar component surged to 19.96 mJ/m 2 . MD simulation results indicate that PAE acts as a molecular bridge, significantly reducing interfacial repulsion between the two phases. The interaction energy increased by approximately 35.6% (reaching 324.4 kcal/mol) compared to the unmodified system. The PAE layer uses a unique “side‐chain anchoring–main‐chain toughening” multiscale dissipation mechanism. As a result, the composite material's mechanical properties have been significantly enhanced. In contrast to the pristine CF/EP, the CF‐PAE‐1/EP displayed marked superiority in mechanical behavior, specifically achieving 960 MPa in flexural strength (~30% growth), 148.54 kJ/m 2 in impact strength (~66.8% growth), and an ILSS of 50.44 MPa.