Constructing a Molecular Pulley Network Interphase for Simultaneous Enhancement of Interfacial Toughness and Strength in Carbon Fiber/Epoxy Composites

Simultaneous enhancement of interfacial toughness and strength in carbon fiber reinforced polymer matrix composites (CFPRs) is critical for achieving superior mechanical performance and long-term durability. Herein, a multi-aldehyde polyrotaxane (maPR) was synthesized and incorporated into the CFRP interphase at varying branched polyethyleneimine (PEI)/maPR ratios to construct a molecular pulley network. The 2:1 PEI/maPR formulation (PEI 2 -PR 1 ) generated an optimal molecular pulley network within the interphase of CFRP, which enhanced stress dissipation capacity while increasing interphase thickness and crosslinking density. Compared to the desized carbon fiber (CF-desized), the PEI 2 -PR 1 -modified carbon fibers (CF-(PEI 2 -PR 1 )) demonstrated significantly increased surface roughness and wettability. Consequently, the CF-(PEI 2 -PR 1 )/EP composite exhibited the widest interphase (402 ± 8 nm), the highest transverse fiber bundle test (TFBT) strength (24.80 ± 2.21 MPa), interfacial shear strength (IFSS) (72.17 ± 2.99 MPa), and interfacial toughness (194.13 ± 2.43 J/m 2 ), along with the optimal release of residual interfacial stress (82.10%). This work proposed a novel and effective approach for simultaneously enhancing the interfacial toughness and strength of CFRP through molecular-scale interphase engineering. Graphical Constructing a molecular pulley network interphase for simultaneous enhancement of the interfacial toughness and strength in carbon fiber/epoxy composites.