3D Printing of Vinylogous Urethane-Based Methacrylic Covalent Adaptable Networks by Vat Photopolymerization

Covalent adaptable networks (CANs) have the potential to combine the excellent mechanical properties of traditional thermoset materials with the reprocessability of traditional thermoplastics. However, the processing of CANs using common techniques for thermoplastics has proven challenging. In this work, the 3D printing of reprocessable CANs with controlled shape is reported using vat photopolymerization (VP). Using a vinylogous urethane-containing methacrylic cross-linker, a series of resins containing nonreactive and reactive diluents are described. The resin viscosity can be easily tuned by the relative amount of diluent to functional cross-linker such that the viscosity of commercial resins can be easily achieved. By studying the curing kinetics using Jacob's equation, optimal printing conditions are found that allow for high-resolution printing with limited shrinkage. In addition, due to the presence of dynamic bonds in the final material, it is shown that the final printed piece can be reprocessed at high temperatures and can even be recycled into a second-generation resin that can be reprinted.