@article{MechauFrankBakircietal.2021,
  author    = {Mechau, Jannik and Frank, Andreas and Bakirci, Ezgi and Gumbel, Simon and Jungst, Tomasz and Giesa, Reiner and Groll, J{\"u}rgen and Dalton, Paul D. and Schmidt, Hans-Werner},
  title     = {Hydrophilic (AB)\(_{n}\) Segmented Copolymers for Melt Extrusion-Based Additive Manufacturing},
  series = {Macromolecular Chemistry and Physics},
  volume    = {222},
  journal   = {Macromolecular Chemistry and Physics},
  number    = {1},
  doi       = {10.1002/macp.202000265},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-224513},
  year      = {2021},
  abstract  = {Several manufacturing technologies beneficially 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 to form physically crosslinked hydrogels after swelling. The 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 adjusted to match the melt viscosity to the different melt-processing techniques. Using extrusion-based printing, a width of approximately 260 µm is printed into 3D constructs, with excellent interlayer bonding at fiber junctions, due to hydrogen bonding between the layers. For melt electrospinning, much thinner fibers in the range of about 1-15 µm are obtained and produced in a typical nonwoven morphology. With melt electrowriting, fibers are deposited in a controlled way to well-defined 3D constructs. In this case, multiple fiber layers fuse together enabling constructs with line width in the range of 70 to 160 µm. If exposed to water the printed constructs swell and form physically crosslinked hydrogels that slowly disintegrate, which is a feature for soluble inks within biofabrication strategies. In this context, cytotoxicity tests confirm the viability of cells and thus demonstrating biocompatibility of this class of copolymers.},
  language  = {en}
}
@article{BakirciFrankGumbeletal.2021,
  author    = {Bakirci, Ezgi and Frank, Andreas and Gumbel, Simon and Otto, Paul F. and F{\"u}rsattel, Eva and Tessmer, Ingrid and Schmidt, Hans-Werner and Dalton, Paul D.},
  title     = {Melt Electrowriting of Amphiphilic Physically Crosslinked Segmented Copolymers},
  series = {Macromolecular Chemistry and Physics},
  volume    = {222},
  journal   = {Macromolecular Chemistry and Physics},
  number    = {22},
  doi       = {10.1002/macp.202100259},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-257572},
  year      = {2021},
  abstract  = {Various (AB)\(_{n}\) and (ABAC)\(_{n}\) segmented copolymers with hydrophilic and hydrophobic segments are processed via melt electrowriting (MEW). Two different (AB)\(_{n}\) segmented copolymers composed of bisurea segments and hydrophobic poly(dimethyl siloxane) (PDMS) or hydrophilic poly(propylene oxide)-poly(ethylene oxide)-poly(propylene oxide) (PPO-PEG-PPO) segments, while the amphiphilic (ABAC)\(_{n}\) segmented copolymers consist of bisurea segments in the combination of hydrophobic PDMS segments and hydrophilic PPO-PEG-PPO segments with different ratios, are explored. All copolymer compositions are processed using the same conditions, including nozzle temperature, applied voltage, and collector distance, while changes in applied pressure and collector speed altered the fiber diameter in the range of 7 and 60 µm. All copolymers showed excellent processability with MEW, well-controlled fiber stacking, and inter-layer bonding. Notably, the surfaces of all four copolymer fibers are very smooth when visualized using scanning electron microscopy. However, the fibers show different roughness demonstrated with atomic force microscopy. The non-cytotoxic copolymers increased L929 fibroblast attachment with increasing PDMS content while the different copolymer compositions result in a spectrum of physical properties.},
  language  = {en}
}