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

Abstract 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.