Solvent-cast 3D printing of polysulfone and polyaniline composites

Polysulfone (PSU) and polysulfone/polyaniline (PANI) composites were 3D printed by solvent-cast direct write deposition. Traditional material extrusion techniques require the application of heat to melt the polymer during extrusion and printing. This type of thermal processing poses potential limitations for printing polymers that have high processing temperatures or thermally degrade. PSU is a thermally stable polymer, but has an elevated glass transition temperature of 185–190 °C and is highly viscous in the melt. On the other hand, polyaniline is a semiconducting polymer that thermally degrades before melting By using solvent-based inks, PSU and PSU/PANI composites were 3D printed at room temperature using direct write deposition. PSU inks consisted of PSU dissolved in a mixture of dichloromethane (DCM) and dimethylformamide (DMF). The DCM evaporated quickly to harden the extruded filament, while the DMF evaporated slowly to allow for a smoother extruded filament and more consistent extrusion with well-bonded layers. Best results were obtained with PSU concentrations at 35–40 wt% with a DCM:DMF volume ratio of 5:1. The optimized PSU/PANI inks consisted of 30 wt% undoped PANI, and 35 wt% doped PANI, with 20 wt% PSU solution in dichloroethane (DCE) used as a binder. Using capillary viscometry it was confirmed that the inks exhibited pseudoplastic behavior, which is expected for polymer solutions and melts. It was shown that objects printed using the PSU/PANI ink are not conductive when undoped PANI was used, but became conductive when the PANI powder was first doped in 1 M H₂SO₄ before printing. A resistivity of 4.83 Ω-m was achieved with an ink containing 35 wt% doped PANI and 13 wt% PSU.