Understanding interfacial interaction characteristics of carbon nitride reinforced epoxy composites from atomistic insights

Two-dimensional carbon nitride (C₃N) is a promising alternative to graphene (GN) as the reinforcement in epoxy composites, yet the complicated interfacial interactions have not been fully understood, which restricts the application of using C₃N for enhancing the mechanical properties of thermosetting polymers. To explore its functionality, we undertake this work aims to overcome the obstacles and uncover the interfacial interaction mechanism between C₃N and epoxy chains through density function theory (DFT) and molecular dynamics (MD) simulations. We discover, for the first time, that C₃N sheet exhibits outstanding performances on improving the thermal-mechanical properties of epoxy composites. The Young's modulus and glass transition temperature of C₃N reinforced epoxy are 20% and 26 K (7%) larger than that of GN filled epoxy, respectively. Our findings conclude that the interfacial interaction mechanisms behind the superlative thermal-mechanical properties are: (1) the C₃N sheet exhibits a better adhesion with aromatic rings of epoxy chains, which is attributed to preferred parallel alignment of aromatic rings and C₃N surface, and (2) the C₃N sheet induces a higher capacity of hydrogen bonding at the interface, leading to better load transfer. The superior reinforcing efficiency of C₃N over GN opens extensive applications of it in the next-generation thermomechanical systems.