Covalent Adaptable Networks and Vitrimer Topology in Vat Photopolymerisation: Exchange Kinetics, Reprocessing and Dimensional Stability
Segurola, Juan
2026-08-27 · Report · Version 1.1
Vat photopolymerisation normally converts a low-viscosity reactive formulation into a permanently crosslinked thermoset whose network topology is effectively fixed after cure. Covalent adaptable networks introduce exchangeable covalent bonds that permit the cured topology to rearrange under a defined stimulus while retaining, or temporarily modifying, network connectivity. This creates routes to stress relaxation, welding, reshaping, repair, hot-press reprocessing, chemical transformation and, in selected systems, preparation of a second-generation printable resin. The engineering opportunity is accompanied by a fundamental conflict. Bond exchange must be sufficiently slow under storage, printing and service conditions to preserve dimensions and load-bearing performance, yet sufficiently rapid under an intended activation condition to enable useful topology rearrangement. The relevant property is therefore not simply the presence of a dynamic bond, but a temperature-time-stress window connecting exchange kinetics, segmental mobility, creep resistance and the geometry of the printed part. Published VPP systems include catalyst-free boronate- ester networks with room-temperature exchange, thermally activated thioester-anhydride systems, transesterification-based acrylate vitrimers, vinylogous-urethane methacrylic networks and bio-based vitrimer formulations. They demonstrate reconfiguration, interfacial welding, reduced mechanical anisotropy, hot- press reprocessing and second-generation resin preparation. The numerical outcomes remain chemistry-, formulation-, geometry- and protocol-specific. This review develops a process-resolved framework for qualifying VPP covalent adaptable networks. It distinguishes associative and dissociative exchange, separates stress relaxation from creep, defines the service-to-reprocessing window, and requires retained dimensions and properties to be reported together with exchange rate. It also separates repair, welding, reshaping, reprocessing, chemical recycling and reprinting, which are frequently conflated in circularity claims.