@phdthesis{Nahm2021,
  author    = {Nahm, Daniel},
  title     = {Poly(2-oxazine) Based Biomaterial Inks for the Additive Manufacturing of Microperiodic Hydrogel Scaffolds},
  doi       = {10.25972/OPUS-24598},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-245987},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2021},
  abstract  = {The aim of this thesis was the preparation of a biomaterial ink for the fabrication of chemically crosslinked hydrogel scaffolds with low micron sized features using melt electrowriting (MEW). By developing a functional polymeric material based on 2-alkyl-2-oxazine (Ozi) and 2-alkyl-2-oxazoline (Ox) homo- and copolymers in combination with Diels-Alder (DA)-based dynamic covalent chemistry, it was possible to achieve this goal. This marks an important step for the additive manufacturing technique melt electrowriting (MEW), as soft and hydrophilic structures become available for the first time. The use of dynamic covalent chemistry is a very elegant and efficient method for consolidating covalent crosslinking with melt processing. It was shown that the high chemical versatility of the Ox and Ozi chemistry offers great potential to control the processing parameters. The established platform offers straight forward potential for modification with biological cues and fluorescent markers. This is essential for advanced biological applications. The physical properties of the material are readily controlled and the potential for 4D-printing was highlighted as well. The developed hydrogel architectures are excellent candidates for 3D cell culture applications. In particular, the low internal strength of some of the scaffolds in combination with the tendency of such constructs to collapse into thin strings could be interesting for the cultivation of muscle or nerve cells. In this context it was also possible to show that MEW printed hydrogel scaffolds can withstand the aspiration and ejection through a cannula. This allows the application as scaffolds for the minimally invasive delivery of implants or functional tissue equivalent structures to various locations in the human body.},
  subject      = {Polymere},
  language  = {en}
}
@phdthesis{Kade2023,
  author    = {Kade, Juliane Carolin},
  title     = {Expanding the Processability of Polymers for a High-Resolution 3D Printing Technology},
  doi       = {10.25972/OPUS-27005},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-270057},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2023},
  abstract  = {This thesis identifies how the printing conditions for a high-resolution additive manufacturing technique, melt electrowriting (MEW), needs to be adjusted to process electroactive polymers (EAPs) into microfibers. Using EAPs based on poly(vinylidene difluoride) (PVDF), their ability to be MEW-processed is studied and expands the list of processable materials for this technology.},
  subject      = {Polymere},
  language  = {en}
}
@phdthesis{Lorson2019,
  author    = {Lorson, Thomas},
  title     = {Novel Poly(2-oxazoline) Based Bioinks},
  doi       = {10.25972/OPUS-18051},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-180514},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2019},
  abstract  = {Motivated by the great potential which is offered by the combination of additive manufacturing and tissue engineering, a novel polymeric bioink platform based on poly(2 oxazoline)s was developed which might help to further advance the young and upcoming field of biofabrication. In the present thesis, the synthesis as well as the characteristics of several diblock copolymers consisting of POx and POzi have been investigated with a special focus on their suitability as bioinks. In general, the copolymerization of 2-oxazolines and 2-oxazines bearing different alkyl side chains was demonstrated to yield polymers in good agreement with the degree of polymerization aimed for and moderate to low dispersities. For every diblock copolymer synthesized during the present study, a more or less pronounced dependency of the dynamic viscosity on temperature could be demonstrated. Diblock copolymers comprising a hydrophilic PMeOx block and a thermoresponsive PnPrOzi block showed temperature induced gelation above a degree of polymerization of 50 and a polymer concentration of 20 wt\%. Such a behavior has never been described before for copolymers solely consisting of poly(cyclic imino ether)s. Physically cross linked hydrogels based on POx b POzi copolymers exhibit reverse thermal gelation properties like described for solutions of PNiPAAm and Pluronic F127. However, by applying SANS, DLS, and SLS it could be demonstrated that the underlying gel formation mechanism is different for POx b POzi based hydrogels. It appears that polymersomes with low polydispersity are formed already at very low polymer concentrations of 6 mg/L. Increasing the polymer concentration resulted in the formation of a bicontinuous sponge like structure which might be formed due to the merger of several vesicles. For longer polymer chains a phase transition into a gyroid structure was postulated and corresponds well with the observed rheological data. Stable hydrogels with an unusually high mechanical strength (G' ~ 4 kPa) have been formed above TGel which could be adjusted over a range of 20 °C by changing the degree of polymerization if maintaining the symmetric polymer architecture. Variations of the chain ends revealed only a minor influence on TGel whereas the influence of the solvent should not be neglected as shown by a comparison of cell culture medium and MilliQ water. Rotationally as well as oscillatory rheological measurements revealed a high suitability for printing as POx b POzi based hydrogels exhibit strong shear thinning behavior in combination with outstanding recovery properties after high shear stress. Cell viability assays (WST-1) of PMeOx b PnPrOzi copolymers against NIH 3T3 fibroblasts and HaCat cells indicated that the polymers were well tolerated by the cells as no dose-dependent cytotoxicity could be observed after 24 h at non-gelling concentrations up to 100 g/L. In summary, copolymers consisting of POx and POzi significantly increased the accessible range of properties of POx based materials. In particular thermogelation of aqueous solutions of diblock copolymers comprising PMeOx and PnPrOzi was never described before for any copolymer consisting solely of POx or POzi. In combination with other characteristics, e.g. very good cytocompatibility at high polymer concentrations and comparably high mechanical strength, the formed hydrogels could be successfully used for 3D bioprinting. Although the results appear promising and the developed hydrogel is a serious bioink candidate, competition is tough and it remains an open question which system or systems will be used in the future.},
  subject      = {Polymere},
  language  = {en}
}