Solvent-Free Room-Temperature DLP 3D Printing of High-Performance Engineering Thermoplastic Cardo Poly(etheretherketone) (PEEK)-Based Resins

Photocurable resin formulations based on high-performance engineering thermoplastic polymers like polyarylether ketones (PAEKs) are rare due to their high aromaticity, which makes them nearly insoluble. In this work, we present a design strategy specifically created for the synthesis of photocurable cardo poly(aryl ether)s, which are derived from a phthalimide-functionalized bisphenol monomer and aromatic dihalide. The cardo polymer (polyetherether ketone containing a bulky side group) underwent postpolymer modification through the introduction of methacrylic groups in each repeat unit. A photocurable formulation was developed by mixing 15 and 20 wt. % of the methacrylic-modified cardo poly(aryl ether) with bisphenol A ethoxylate dimethacrylate (BPAEDMA) and hydroxyethyl methacrylate (HEMA) as a reactive diluent, along with 1 wt. % of diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO) as the photoinitiator, making them suitable for DLP 3D printing. To our knowledge, this is the first report of the inclusion of cardo poly(aryl ether)s into photocurable monomers. The resulting 3D-printed objects exhibited remarkable thermal and mechanical properties, with the 20 wt. % cardo PEEK formulation exhibiting a tensile strength of 75 ± 4 MPa, comparable to that of the tensile strength of FDM 3D-printed pure PEEK filament. This is quite remarkable, as DLP 3D printing can be performed at room temperature with excellent resolution for the 3D-printed objects, unlike FDM 3D printing. Furthermore, 3D-printed parts containing the cardo poly(aryl ether) polymer displayed intrinsic fluorescence under UV light without requiring external fluorescent dyes.