Melt electrowriting of thermoplastic polycarbonate-silicone polyurethanes: From polymer design to microfiber fabrication

Melt electrowriting (MEW) is an additive manufacturing technique that has gained significant attention due to its ability for controlled fabrication of microfiber architectures, however wider application is hindered by its still limited material library. Materials such as thermoplastic polyurethanes (TPUs) remain a challenge, due to temperature-induced degradation and crosslinking when kept in the melt in the cartridge over the long residence times due to the low volume flow rate of MEW. Here, we introduced for the first time a newly synthesized thermoplastic polycarbonate-silicone polyurethane (TPCSUs) for MEW, obtained by the addition of silicone as second soft segment to thermoplastic polycarbonate-urethanes. We showed the influence of the chemistry of diisocyanate and of the fraction of hard segment on the printability and identified a hydrogenated methylene diphenyl diisocyanate (HMDI)-based TPCSU that did not crosslink when kept in a melt at 200 °C. Constructs were successfully melt-electrowritten with a target fiber diameter range of 10–50 μm. With the progressing thermal degradation over longer printing times, the constructs exhibited macromolecule chain scission, crystallinity increase, and glass temperature decrease. A printability time-window of 3 h was defined suitable for MEW, exhibiting no significant changes in fiber diameter, print accuracy, and E-modulus of the constructs. The hemocompatibility endowed by the silicone and the antibacterial properties were also maintained. Longer residence times resulted in print defects of increasing severity. This study introduces a comprehensive characterization of TPCSU MEW constructs over the printing time and emphasizes the role of adjusting the macromolecular composition to achieve MEW processability. • TPCSU with PDMS/PC as soft segment, and HMDI/BDO as hard segment was synthesized. • TPCSU kept in the melt state did not crosslink and was processed by melt electrowriting (MEW). • TPCSU constructs with defined microfiber architectures were produced by MEW. • Printability time-window of 3 h resulted in constant construct properties and print accuracy. • MEW constructs showed good hemocompatibility, and low bacterial adhesion.