Konstanze Seidler - Academia.edu (original) (raw)

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Papers by Konstanze Seidler

Cardiovascular Pathology, 2013

ABSTRACT Due to innate surface thrombogenicity and biomechanical mismatch with the host vessels, ... more ABSTRACT Due to innate surface thrombogenicity and biomechanical mismatch with the host vessels, currently used synthetic conduits, such as ePTFE, are prone to thrombosis and intimal hyperplasia formation. To overcome these limitations, biodegradable scaffolds, with the potential to induce regenerative remodelling, are considered. We evaluated the application of new biodegradable, thermoplastic polyurethane (aTPU) and ePTFE vascular prostheses.

Journal of Materials Chemistry A

Investigation of a cyanate ester based formulation and stereolithography-based additive manufactu... more Investigation of a cyanate ester based formulation and stereolithography-based additive manufacturing via Hot Lithography to produce polycyanurates with a glass transition temperature of 336 °C without any additives.

Journal of Polymer Science Part A: Polymer Chemistry, 2018

Thermoplastic polyurethane elastomers (TPUs) with a biodegradable chain extender and different no... more Thermoplastic polyurethane elastomers (TPUs) with a biodegradable chain extender and different nonaromatic diisocyanate hard segments were synthesized and tested concerning their thermal, mechanical, and degradation properties and for their processability regarding electrospinning. The design of the TPUs was based on the structural modification of the hard segment using linear aliphatic hexamethylene diisocyanate (HMDI), more rigid alicyclic 4,4 0-methylene bis(cyclohexylisocyanate) (H12MDI), 1,3-bis (isocyanatomethyl)cyclohexane (BIMC), or isophorone diisocyanate (IPDI). The soft segment consisted of poly(tetrahydrofuran). Bis(2-hydroxyethyl) terephthalate (BET) was used as chain extender with cleavable ester bonds. Some of the polyurethanes based on alicyclic diisocyanate showed better mechanical performance than the less rigid HMDI-based TPU. The TPU in vitro degradability was tested for 25 days at elevated temperatures in PBS buffer and indicated a bulk erosion process. Electrospinning experiments were conducted and promising results with respect to further applicability of these materials in vascular tissue engineering were obtained.

Polymer Chemistry, 2016

Vinyl sulfone esters are described as a new class of AFCT reagents for methacrylate-based photopo... more Vinyl sulfone esters are described as a new class of AFCT reagents for methacrylate-based photopolymerization without the drawback of retardation but good regulation of network architecture. Resulting materials show low shrinkage stress and increased toughness. This paves the way for vinyl sulfone esters in lithography-based 3D printing.

Advanced Engineering Materials

Die Erfindung betrifft die Verwendung von Sulfonsaureestern der nachstehenden Formel 1 und/oder F... more Die Erfindung betrifft die Verwendung von Sulfonsaureestern der nachstehenden Formel 1 und/oder Formel 2, einzeln oder als Gemisch mehrerer davon, als Regler bei Polymerisationsreaktionen von radikalisch polymerisierbaren, ethylenisch ungesattigten Monomeren: worin A jeweils unabhangig ausgewahlt ist aus H, CN, linearen, verzweigten oder zyklischen aliphatischen oder aromatischen C 1 -C 30 -Kohlenwasserstoffresten; X jeweils unabhangig -COO- oder -CON(R 1 )- ist, wobei die Bindung an A uber O oder N erfolgt, oder fehlt, wenn A ein aromatischer Kohlenwasserstoffrest oder CN ist; B jeweils unabhangig ausgewahlt ist aus linearen, verzweigten oder zyklischen aliphatischen oder aromatischen C 1 -C 30 -Kohlenwasserstoffresten; R 1 jeweils unabhangig ausgewahlt ist aus Wasserstoff und linearen, verzweigten oder zyklischen aliphatischen oder aromatischen C 1 -C 10 -Kohlenwasserstoffresten, die gegebenenfalls mit einer oder mehreren OH-Gruppen substituiert sind, wobei die aliphatischen Kohle...

Polymer, 2018

Chain transfer reagents serve as a valuable tool for the modification of methacrylate-based photo... more Chain transfer reagents serve as a valuable tool for the modification of methacrylate-based photopolymer networks. Employment of such chemistry enables easy tuning of mechanical and thermomechanical network properties, thus potentially widens the field of application for such crosslinked polymer networks. Thiols are the most prominent class of chain transfer reagent and possess a great number of favorable characteristics (e.g., high conversion, reduced shrinkage stress, or high toughness, meaning the combination of high tensile strength and impact resistance). Mostly, thiols with higher functionality are used for network formation as monomer leaching and thinning effects are crucial drawbacks of monofunctional additives. Addition fragmentation chain transfer (AFCT) reagents (e.g., vinyl sulfonate esters) have been recently introduced as powerful network regulators for methacrylate-based photopolymerization. After successful synthesis of a difunctional vinyl sulfonate ester the photoreactivity in methacrylate-based systems was compared to an equivalent thiol-ene system. Through the introduction of a difunctional vinyl sulfonate ester-derivative, homogeneous photopolymer networks with high conversions, reduced shrinkage stress, tunable crosslink density and thermomechanical properties were fabricated. The final materials exhibit high hardness, tensile strength and gel content as well as improved impact resistance.

Journal of Polymer Science Part A: Polymer Chemistry, 2015

The rapid and uncontrolled nature of network formation from di(meth)acrylate monomers produces hi... more The rapid and uncontrolled nature of network formation from di(meth)acrylate monomers produces high shrinkage stress and results in polymers with oftentimes brittle mechanical properties. Methods for regulating polymerization and network formation are sought. One option is the use of addition-fragmentation chain transfer (AFCT) agents, which are well known to control molecular weight and molecular weight distribution of monofunctional (meth)acrylates. A series of novel and previously described AFCT reagents were synthesized and screened with laser flash photolysis to determine reactivity. Well-performing AFCT reagents were then tested in polymerizations with monofunctional and difunctional methacrylates. With monofunctional monomers, the molecular weight and polydispersity of the resultant linear polymers tend to decrease with the addition of AFCT agent. In copolymerization with dimethacrylate monomers, the AFCT agents were found to substantially lower and sharpen the glass transition. Sharpness of the glass transition is here indicative of a more regular and homogenous network. After coupling of the instruments, photorheology was performed simultaneously with real-time IR to show an increase in monomer conversion at the time of gelation, which appears to have a positive effect on reducing shrinkage stress. V

Journal of Polymer Science Part A: Polymer Chemistry, 2011

Thermoplastic polyurethane (TPU) elastomers with biodegradable chain extenders were synthesized a... more Thermoplastic polyurethane (TPU) elastomers with biodegradable chain extenders were synthesized and tested for mechanical performance and biocompatibility. The design of the TPUs was based on structural modification of a mechanically appropriate aromatic isocyanate-based TPU. As the aromatic isocyanate was substituted with a less toxic but also less ''hard'' aliphatic isocyanate, the chain extender plays an important role on the mechanical properties. Here, the terephthalate ester chain extender was found to work better than hydroxyl ethyl lactate in providing polymers with mechanical properties similar to commercial aromatic isocyanate-based TPUs. The polymers were degraded in aqueous solutions at elevated temperatures and compared to polylactic acid (PLA) to partially simulate biodegradation. The lactate-based TPUs degraded about twice as fast as PLA while the terephthalate-based TPU degraded much more slowly. The latter material was processed by electrospinning to give a tubular graft approximately the size of a large rat blood vessel. Initial results from implantation of these TPUs into rats are promising and indicate that biodegradation occurs and is likely beneficial to cell proliferation. V

Applied Materials Today, 2021

Abstract Through history, numerous art, religious and every-day objects were carved from ivory be... more Abstract Through history, numerous art, religious and every-day objects were carved from ivory because of its aesthetic appearance, convenient workability and its durability. Since the ivory trading ban was passed in 1989, many natural and synthetic materials were introduced as a replacement, but these are typically only available in bulk. To restore sometimes very complex and delicate artefacts, it is economically reasonable to develop a substitute that can be built by additive manufacturing to reduce carving time and material waste. Such a substitute material should especially mimic the aesthetic characteristics of ivory by means of the colour, translucency and surface gloss. All merchantable 3D printable substitute materials have evidential limitations in exactly those important characteristics. The newly developed substitute material called "Digory" is processible with an additive manufacturing technique that derived from stereolithography. Layer by layer, a photosensitive slurry that consists mainly of a dimethacrylic resin filled with calcium phosphate particles is polymerized with a UV laser. The solids loading, which was adjusted to fit the translucency of ivory, was around 30 vol.%. At this content, the density of about 1.79 g cm−3 and the hardness of 35.7 HV0.2 are equivalent to the values for ivory found in the literature. Small quantities of yellow and red colour pigments were used to modify the basic colour. With further post-processing using traditional handcraft techniques, such as staining and polishing of the surface, an optical imitation of natural ivory was achieved.

Polymer Chemistry, 2022

Additive manufacturing of phenolic resins as a proof-of-concept for the first photo-chemical indu... more Additive manufacturing of phenolic resins as a proof-of-concept for the first photo-chemical induced polycondensation by Hot Lithography. Through the dual use of a photoacidgenerator, the first pure 3D printing of Bakelite© is investigated.

Angewandte Chemie (International ed. in English), Jan 16, 2018

The formation of networks through light-initiated radical polymerization allows little freedom fo... more The formation of networks through light-initiated radical polymerization allows little freedom for tailored network design. The resulting inhomogeneous network architectures and brittle material behavior of such glassy-type networks limit the commercial application of photopolymers in 3D printing, biomedicine, and microelectronics. An ester-activated vinyl sulfonate ester (EVS) is presented for the rapid formation of tailored methacrylate-based networks. The chain transfer step induced by EVS reduces the kinetic chain length of the photopolymer, thus shifting the gel point to higher conversion, which results in reduced shrinkage stress and higher overall conversion. The resulting, more homogeneous network is responsible for the high toughness of the material. The unique property of EVS to promote nearly retardation-free polymerization can be attributed to the fact that after the transfer step no polymerizable double bond is formed, as is usually seen in classical chain transfer agen...