Jörg Kressler

Hydrogels were prepared by Steglich esterification and by crosslinking pre-synthesized poly(sorbitol adipate)-graft-poly(ethylene glycol) mono methyl ether (PSA-g-mPEG) using different-chain-length-based disuccinyl PEG. PSA and PSA-g-mPEG were investigated for polymer degradation as a function of time at different temperatures. PSA-g-mPEG hydrogels were then evaluated for their most crucial properties of swelling that rendered them suitable for many pharmaceutical and biomedical applications. Hydrogels were also examined for their Sol-Gel content in order to investigate the degree of cross-linking. Physical structural parameters of the hydrogels were theoretically estimated using the modified Flory–Rehner theory to obtain approximate values of polymer volume fraction, the molecular weight between two crosslinks, and the mesh size of the hydrogels. X-ray diffraction was conducted to detect the presence or absence of crystalline regions in the hydrogels. PSA-g-mPEG hydrogels were then extensively examined for higher and lower molecular weight solute release through analysis by fluorescence spectroscopy. Finally, the cytotoxicity of the hydrogels was also investigated using a resazurin reduction assay. Experimental results show that PSA-g-mPEG provides an option as a biocompatible polymer to be used for pharmaceutical applications.

Poly(ethylene glycol) (PEG) based networks have been used extensively for biomedical applications and as solid state electrolytes. In this work, a series of PEG networks was prepared using bifunctional PEG of molar mass 400, 1000, 2000, 4000, and 6000 g mol −1 and star shaped PEG ( M n = 1000 g mol −1 ) cross‐linker using copper‐catalyzed Huisgen 1,3‐dipolar cycloaddition or “click” chemistry. The end‐group modification of the bifunctional polymers and the star shaped cross‐linker with alkyne and azide groups, respectively, was confirmed by 1 H NMR spectroscopy. The coupling reaction between azide and alkyne functionalities for the network formation was confirmed by Fourier transform infrared (FTIR) spectroscopy. The thermal properties of polymer network were determined by differential scanning calorimetry. Swelling studies of the networks were performed to correlate the network structure with the physical properties. The molar mass between the cross‐links was determined using the Bray‐Merill modified Flory‐Rehner equation. The effect of molar mass between the cross‐linking points on the strength of the networks was compared. Additionally, the effect of the stoichiometry of the precursors on the network strength was also studied. Finally, thickness‐dependent tensile testing was performed to investigate the stress oscillation phenomenon.