|Mechau, J.; Frank, A.; Bakirci, E.; Gumbel, S.; Jungst, T.; Giesa, R.; Groll, J.; Dalton, P.D.; Schmidt, H.-W.: Hydrophilic (AB)n segmented copolymers for melt extrusion based additive manufacturing, Macromolecular Chemistry and Physics, 222(1), 2000265 (2020) -- DOI: 10.1002/macp.202000265|
There are several manufacturing technologies that can involve processing from the melt, including extrusion-based printing, electrospinning and electrohydrodynamic jetting. In this study, (AB)n segmented copolymers are tailored for melt-processing with these different techniques, to produce physically crosslinked hydrogels after swelling. The (AB)n segmented copolymers are composed of hydrophilic poly(ethylene glycol) based segments and hydrophobic bisurea segments, which form physical crosslinks via hydrogen bonds. The degree of polymerization was adapted in order to vary the melt viscosity, required by the different melt processing techniques. Using extrusion-based printing we can direct-write with a typical line width of about 260 μm and layer these into 3D constructs. The interlayer bonding quality at fiber junctions is excellent, due to hydrogen bonding between the layers. Using melt electrospinning, much thinner fibers in the range of about 1 to 15 μm are obtained, produced in a typical non-woven morphology. With melt electrowriting, the fibers are deposited in a controlled way and well-defined 3D constructs are produced. In this case, multiple fibers fuse into each other to produce fiber diameters from 70 to 160 μm. If exposed to water the hydrophilic segments of all products swell and form physically-crosslinked hydrogels that slowly disintegrate, which is an interesting feature for soluble inks within biofabrication strategies. In this respect, we performed cytotoxicity tests and demonstrate the viability of cells and thus the biocompatibility of this class of (AB)n segmented copolymers.