Heat-Resistant Phthalonitrile-Based Resins for 3D Printing via Vat Photopolymerization

In this study, a maleimide/phthalonitrile bifunctional monomer PNB-M was used in vat photopolymerization via the maleimide group to obtain phthalonitrile-containing polymers suitable for further thermal postcuring. A high concentration (40 wt %) and low viscosity (less than 500 mPa·s at 25 °C) photopolymer resin was prepared from the phthalonitrile monomer PNB-M with 4-acryloylmorpholine as comonomer and trimethylolpropane trimethacrylate as cross-linker. Photo-DSC, NMR, and FTIR tests revealed free-radical photoinduced copolymerization of the maleimide with the acrylic groups during 3D printing. Postprinting thermal curing of the phthalonitrile groups was performed with different curing agents as well as via self-initiation by PNB-M. The developed phthalonitrile-containing polymerizable compositions made it possible to increase glass transition temperatures of the 3D printed polymer materials up to 351 °C after additional thermal postcuring. Moreover, mechanical properties of the 3D printed materials have been improved after curing of the phthalonitrile monomer in the maleimide–acrylate copolymer.