Dynamically crosslinked-interpenetrating networks for sustainable 3D-printed elastomeric foams

Hierarchically structured elastomeric foams, fabricated via 3D printing, combine the lightweight properties of conventional foams with the design versatility of additive manufacturing, offering significant potential for applications in energy absorption, vibration damping, and flexible sensing. However, vat photopolymerization 3D-printed materials, despite their superior resolution and interlayer adhesion, face challenges in eco-friendly supercritical fluid foaming due to excessive crosslinking density. Here, we present a photocurable resin system incorporating dynamic hindered urea bonds within a polyurethane acrylate matrix, combined with amine-based curing agents. During integrated photocuring and supercritical fluid foaming, this system forms a dynamically crosslinked-interpenetrating network through high-molecular-weight polyurethane/polyurea chains, markedly enhancing foaming performance. The resulting elastomeric foam exhibits uniform, crack-free microcellular architecture, with a high tensile strength of 5.5 MPa, an elongation at break of 510.8%, and exceptional resilience (67.5% drop ball rebound rate and 1.7% residual strain). Furthermore, the elastomeric foam demonstrates excellent recyclability, allowing for multiple cycles of reprocessing and re-foaming. After hot-pressing into elastomers, recycled material maintains a tensile strength of 8.9 MPa and elongation of 965.5%. This approach provides a sustainable route to fabricating high-performance, recyclable hierarchically porous materials.