Computational exploration of the structure and mechanical behaviour of hybrid epoxy-acrylate dual-cure systems.

Abstract

Wavelength-selective dual-cure epoxy-acrylate polymers have recently been demonstrated experimentally as a platform for generating large mechanical contrasts from a single material system for additive manufacturing [Kim et al., Nat. Mater., 2025, 24, 1116-1125], motivating the need for a molecular-level understanding of how network structure and crosslinking governs the mechanical response in such hybrid systems. Here, we use coarse-grained molecular dynamics simulations to investigate the structural, thermal, and mechanical evolution of a model hybrid epoxy-acrylate network spanning elastomeric and thermoset regimes. By systematically varying network architecture, chain length, bond stiffness, and epoxy conversion, we show that elastomer stiffness is highly sensitive to the topology of the initial acrylate network, whereas thermoset stiffness becomes largely insensitive to these structural details once dense epoxy connectivity is established. Tracking network evolution across epoxy conversion reveals a transition that emerges beyond approximately 40% epoxy crosslinking, after the formation of a system-spanning elastomeric network, where network topology becomes increasingly heterogeneous and deformation mechanisms shift from predominantly entropic elasticity to energy-dominated load transfer involving localized covalent bond stretching. This crossover marks the onset of thermoset-like load transfer, with subsequent crosslinking further strengthening this response as stiffness and bond-level deformation increase smoothly. Together, these results provide a framework for understanding how mechanical contrast in wavelength-selective dual-cure polymer networks emerges from the interplay between elastomeric network topology and a connectivity-driven crossover in deformation mechanisms induced by epoxy crosslinking.