Solution‐Based 3D Printing of Polymers of Intrinsic Microporosity

Abstract

Current additive manufacturing methods have significant limitations in the classes of compatible polymers. Many polymers of significant technological interest cannot currently be 3D printed. Here, a generalizable method for 3D printing of viscous tenary polymer solutions (polymer/solvent/nonsolvent) is applied to both "intrinsically porous" (a polymer of intrinsic microporosity, PIM-1) and "intrinsically nonporous" (cellulose acetate) polymers. Successful ternary ink formulations require balancing of solution thermodynamics (phase separation), mass transfer (solvent evaporation), and rheology. As a demonstration, a microporous polymer (PIM-1) incompatible 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 contactors (1.27 cm) can fully purify (<1 ppm) toluene vapor (1000 ppm) in N gas for 1.7 h, which is six times longer than PIM-1 in traditional structures, and more than 4000 times the residence time of gas in the contactor. This solution-based additive manufacturing approach greatly extends the range of 3D-printable materials.

A guide to solution‐based additive manufacturing of polymeric structures: Ink design, porosity manipulation, and printing strategy

“…Alternatively, solution-based additive manufacturing (SBAM) deposits the polymer in the form of a ternary solution (ie, polymer, solvent, and nonsolvent), which is also referred to as a "ternary ink." [1] As illustrated in Figure 1, SBAM fabricates objects via layer-by-layer deposition of ternary ink filaments, similar to other processes. This approach is inspired by other solution-processing approaches, most notably, hollow fiber membrane spinning in the dry-jet, wet-quench configuration, in which polymer solution is extruded into a nonsolvent quench bath where it undergoes nonsolvent-induced phase inversion.…”

“…Additive manufacturing techniques enable rapid production of complex structures and is a powerful tool to aid precise architectural engineering of structured materials for applications that require controlled transport phenomena (heat and mass) or mechanical properties. [1] Compared with traditional manufacturing methods, the cost of additive manufacturing scales much less strongly with the object complexity. [2][3][4] Current state-of-the-art additive manufacturing techniques for polymeric materials are capable of processing photoreactive resin, photopolymer inks, thermoplastics, and elastomers via stereolithography, [2,4] PolyJet, [5,6] fused deposition method, [7,8] and direct ink writing (DIW), [9,10] respectively.…”

“…cannot be processed without chemical modification or additional matrix/binder polymers via existing additive manufacturing techniques. [1,13] Several of these functional polymers are currently processed in the form of polymer solutions. [14][15][16][17][18] By dissolving polymers in their corresponding solvents (such a solution is referred to as a "binary solution" or a "binary ink" in the remainder of this paper), these polymers can be fabricated on an industrial scale into pellets, fibers, and films through solvent evaporation.…”

“…This leads to filament shrinkage, which especially when it occurs in the lateral dimension can result in significant deformation of the filaments and the overall printed object. [1] Differential shrinkage between subsequent layers can cause stresses that are difficult to control and predict. Therefore, this greatly impairs the precision of shape and size of the printed objects.…”

“…In our previous research, various objects made of PIM-1 (polymer of intrinsic microporosity 1) were 3D printed via SBAM. [1] The printed PIM-1 objects possess hierarchical micro-/meso-/macropores (by IUPAC definition, this nomenclature refers to pores with a diameter below 2 nm, between 2 and 50 nm, and above 50 nm, respectively) and exhibit potential for mass transfer applications. [1] Besides PIM-1, other solution-processable polymers such as cellulose acetate have also been 3D printed via SBAM.…”