Decoupling Rigidity and Toughness in Densely Crosslinked Epoxy Networks via Polar Filling and Topological Interlocking

Abstract Axial compressive failure, primarily initiated by fiber microbuckling, severely limits the advanced structural applications of carbon-fiber-reinforced polymer (CFRP) composites. While compressive stiffness in the polymer matrix remains essential to provide robust lateral support, traditional highly cross-linked rigid epoxy networks inevitably succumb to the classic rigidity-brittleness trade-off. Large intrinsic free volumes render these materials highly susceptible to severe volumetric collapse and matrix crushing under extreme compressive loads. Herein, a molecular engineering strategy integrating subnanometer polar filling and topological interlocking addresses this fundamental limitation. Specifically, the synthesis of a novel DMBE epoxy monomer incorporates polar methoxy side groups appended onto a rigid biphenyl backbone. Multiscale characterizations and nonequilibrium molecular dynamics simulations reveal that these pendant methoxy groups act as nanoscale wedges. These moieties achieve precise subnanometer physical filling of the inherent topological voids within the rigid network without expanding the free volume, generating a dense dynamic hydrogen bonding network. Consequently, the neat DMBE resin exhibits an extraordinary compressive yield strength of 253.2 MPa and a modulus of 5131.9 MPa. This study provides a fundamental physical perspective on confined chain dynamics and establishes a revolutionary molecular design paradigm for next-generation, deformation-resistant advanced structural polymers.