Tunable physicochemical properties of 3D printed membranes via copolymerization and micropatterning

3D printing presents significant advantages for membrane fabrication, offering unprecedented control over geometry. Vat photopolymerization (VPP) combined with polymerization-induced phase separation (VPP-PIPS) is a promising method for 3D printing of polymeric membranes, enabling the rapid fabrication of geometrically complex structures. VPP-PIPS utilizes thermoset materials, expanding the range of applicable polymers and providing unique properties such as high chemical and thermal stability. However, the inherent brittleness of thermosets poses a challenge for membrane applications. This study demonstrates that copolymerizing hydroxyethyl methacrylate (HEMA)-based membranes with varying amounts of polyurethane acrylate (PUA) significantly and progressively enhances thermal stability, tensile strength, and hydrophobicity in a tuneable manner, surpassing that of conventional membranes. The thermal stability increases from 260 °C to 345 °C, tensile strength improves from 1.95 MPa to 21.20 MPa, and the contact angle rises from 44.3° ± 4.0°–66.2° ± 3.2°. As the physicochemical properties of VPP-PIPS membranes evolve, membrane characteristics such as porosity, permeability, and pore size also change. With increasing PUA content, porosity decreases from 0.65 ± 0.01 to 0.47 ± 0.03, mean pore size reduces from 171 nm to 46 nm, and permeability drops from 180 ± 19.07 LMH/bar to 0.52 ± 0.14 LMH/bar. Additionally, substituting HEMA with tert-butyl acrylate further increases the contact angle to 108.8 ± 2.6°, while the introduction of 3D micropillars further elevates it to 136.8 ± 1.0°, resulting in a full tuneable range from 44.3° to 136.8 ± 1.0°. These findings highlight the versatility of VPP-PIPS for fabricating membranes with highly customizable properties, paving the way for improved performance in various separation processes.