Polyketimine Covalent Adaptable Networks from Vinyl Monomers via a Free-Radical Approach

We report a radical-mediated one-pot strategy to synthesize polyimine colvalent adaptable networks (CANs) using a formamide-functionalized methacrylate (FEMA) monomer that generates reactive isocyanides in situ for imine bond formation. This approach bypasses the conventional amine–aldehyde condensation, thereby preventing water release and suppressing amine-mediated side reactions. Copolymerization of FEMA with vinyl monomers such as methyl methacrylate (MMA) results in a polyketimine CAN, hence expanding the synthetic tool kit. The added chain-transfer agent refines network uniformity, and the ketimine structure leads to a high activation energy (∼103 kJ/mol). The resulting PMMA CAN exhibits a 23 °C increase in glass transition temperature and excellent creep resistance compared to conventional PMMA. Furthermore, the CANs retain the Young’s modulus and hardness after repeated thermal reprocessing. Detailed stress relaxation experiments and oscillatory shear experiments fully characterize the viscoelastic properties of the CANs. We further show that the transimination reaction can effectively degrade the CANs while offering the advantage of increased resistance to hydrolytic degradation due to ketimine links.