(356b) Solution-Based 3D Printing of Hierarchical Porous Polymers

Current additive manufacturing methods have strong limitations in the classes of polymers that can be printed. This means that many polymers of significant technological interest cannot currently be 3D printed. Here, we demonstrate a generalizable method for 3D printing of viscoelastic polymer solutions and apply it to both porous (a polymer of intrinsic microporosity, PIM-1) and non-porous (cellulose acetate) polymers. Successful ternary ink formulations that result in the creation of three-dimensional structures with hierarchical porosity require balancing of solution thermodynamics (phase separation), mass transfer (solvent evaporation), and rheology. To demonstrate the utility of this approach, a microporous polymer (PIM-1) that cannot be printed with current additive manufacturing technologies is 3D printed into a high-efficiency mass transfer contactor exhibiting hierarchical porosity ranging from sub-nanometer to millimeter pores. Short beds (1.27 cm) of these contactors were challenged with a flow of toluene vapor (1000 ppm) in N₂ gas. These contactors were found to create a pure (< 1 ppm toluene) N₂ stream for 1.7 hours, 6 times longer than traditional structures fabricated from the same PIM-1 material, and more than 4,000 times the residence time of gas in the bed. This solution-based additive manufacturing approach greatly extends the range of materials compatible with 3D printing.