Liane Häussler

Synthesis and characterization of new pH- and thermo-responsive hydrogels based on N-isopropylacrylamide and 2-oxazolines

New pH- and thermo-responsive hydrogels (HG) were synthesized by free radical polymerization of N-isopropylacrylamide and a macromonomer, which was a hydrolyzed random copolymer of 2-carboxyethyl- and 2-methyl-2-oxazoline, using a bisacrylamide as crosslinker. The polymerization was carried out in a mixture of water and ethanol at room temperature and was initiated by ammonium peroxodisulfate. The HG showed conformational transitions with variation of temperature and/or pH-value and as a function of hydrogel composition. This property was shown macroscopically as hydrogel contraction or expansion. The HG structures were characterized by high-resolution magic angle spinning (HRMAS) NMR spectroscopy. The thermal properties, in particular the lower critical solution temperatures, were determined by temperature-dependent HRMAS NMR measurements and differential scanning calorimetry. The pH responsibility was determined by swelling experiments in water at different pH values.

Properties of Segmented Block Copolymers in PEEK/PSU Blends

As a method of compatibilization of immiscible polyether ether ketone (PEEK)/polysulfone (PSU) blends, the addition of segmented PEEK/PSU block copolymers based on amorphous bisphenol A-containing PEEK was studied. This approach was evaluated for blends consisting of PEEK and PSU homopolymers with different molecular weights and different amounts of compatibilizers (segmented PEEK/PSU block copolymers and reactive end-functionalized PEEK and PSU oligomers). The compatibilizers were added under varying melt-processing conditions and effectively allowed the homopolymers to interact with the segmented block copolymers in the blend. The influence of the compatibilizers on the phase behavior was examined in both binary and ternary blends. Interactions in the amorphous phase, which effectively induce an enhancement of the toughness properties of the final product, could be detected.

Melt Spinning of Poly(3‐hydroxybutyrate) for Tissue Engineering Using Electron‐Beam‐Irradiated Poly(3‐hydroxybutyrate) as Nucleation Agent

Electron-beam-irradiated poly(3-hydroxybutyrate) was used as a nucleating agent for poly(3-hydroxybutyrate) in a melt-spinning process. Molecular data and thermal properties of the irradiated samples were determined. The thermal properties of the nucleated melts were determined to assess the influence of the nucleation agents, and then spinning tests were carried out. Thermal and textile properties of the spun fibers were also determined. Estimations of the improvement of the crystallization in the spinline and of the inhibition of secondary crystallization in the fibers from the use of the described blood-compatible nucleation agents are given.

Investigation of Structure and Mechanical Behavior of Polyamide 6/ZnO and Polyamide 6/Al2O3 Nanocomposites

In this work we investigate mechanical properties and structure of PA6/ZnO and PA6/Al2O3 nanocomposites to understand the effect of different nanoparticles on the polymer matrix. Mechanical experiment results show that the mechanical reinforcement effect after loading ZnO nanoparticles is better than that of loading Al2O3 nanoparticles. At 10% ZnO loading, the elastic modulus increases to about two times of that of pure PA6, and the yield stress increases about 30%. And the elongation at break has no obvious decrease even at high ZnO loading. In order to understand the reason of better mechanical reinforcement after incorporating ZnO nanoparticles, microstructure and crystallization behavior of the samples were investigated. The results indicate that the better reinforcement of mechanical properties after loading ZnO was attributed to enhanced interfacial adhesion between ZnO nanoparticles and PA6 matrix at high ZnO content.

Acicular precipitated calcium carbonate as inorganic whisker for reinforcing of polypropylene fibers

Abstract Acicular precipitated calcium carbonate (PCC) was used as appropriate inorganic whisker for improving the mechanical properties of melt spun polypropylene fibers. Nucleation effects of the PCC in dependence to concentration, surface coating and pre-shearing were analyzed. Melt-spinning experiments were carried out in order to determine the reinforcing effect.