Pendant chain strategy endows P-CDs-cured epoxy vitrimer with simultaneous enhancement of strength-toughness, flame retardancy, and recyclability

Three structurally distinct modifiers serving as pendant chains were incorporated into a DOPO-functionalized carbon dot (P-CDs)-cured epoxy vitrimer system, effectively regulating its network topology, intermolecular interactions, and transesterification behavior. • The BnVIm[Cl] pendant chain introduced synergistic cation-π and π-π intermolecular interactions, which significantly strengthened intermolecular forces and endowed the composite with excellent mechanical performances (tensile strength of 64.3 MPa, elongation at break of 15.6%, and toughness of 6.1 MJ/m 3 ). • The imidazole ring in the modifier promoted the carbonization of the EP/CDs/BnVIm[Cl] composite during combustion. The optimized composite achieved superior flame retardancy with a high LOI of 32.6% and UL-94 V-0 rating, accompanied by reduced pHRR, THR, and TSP values. • The EP/CDs/BnVIm[Cl]/CF carbon fiber composite exhibited efficient matrix degradation and outstanding recyclability of carbon fibers, realizing effective fiber recycling. Dynamic epoxy vitrimers feature outstanding reprocessability, self-healing performance, and recyclability. Nevertheless, the improved chain mobility derived from dynamic networks typically deteriorates their mechanical properties. Moreover, achieving high flame retardancy without compromising mechanical performance remains a formidable challenge. Herein, three structurally different pendant chains, namely BnVIm[Cl], VIm[Cl], and Bn, were incorporated into a DOPO-functionalized carbon dot (P-CDs)-cured epoxy vitrimer system to modulate its network topology, intermolecular interactions, and transesterification behavior. The results demonstrated that the EP/CDs/BnVIm[Cl]-7 composite delivered optimal comprehensive performance, with a tensile strength of 64.3 MPa, an elongation at break of 15.6%, and a toughness of 6.1 MJ/m 3 . Meanwhile, it exhibited superior flame retardancy, achieving a limiting oxygen index (LOI) of 32.6% and a UL-94 V-0 rating. The peak heat release rate (pHRR), total heat release (THR), and total smoke production (TSP) were reduced by 30.1%, 13.9%, and 18.9%, respectively. Furthermore, EP/CDs/BnVIm[Cl]-7 exhibited rapid stress relaxation, a crack-closure efficiency of 95.23%, a reprocessing efficiency of 93.39%, and effective solvent-mediated degradability, which enabled efficient resin removal and carbon fiber recovery. The structure-property relationship analysis indicates that the synergistic cation-π and π-π interactions introduced by BnVIm[Cl] strengthen intermolecular forces and increase the effective crosslinking density. Combined with the dynamic β-hydroxyl ester network, a favorable balance between network stability and chain mobility is realized, thereby simultaneously improving the mechanical properties, flame retardancy, and dynamic adaptability of the epoxy vitrimer. Download: Download high-res image (144KB) Download: Download full-size image