Transient Behaviour of Functionalized Polymeric Networks (Funktionspolymere)
Final Report Abstract
The aim of this project was to investigate, experimentally and theoretically, the transient processes in hydrogels. The thermosensitive non-ionic poly(N-isopropylacrylamide) (poly(NIPAAm)) hydrogel was synthesized by free radical polymerization with different cross-linking ratios. It was used to study the release kinetics of BSA and phenol by thermal deswelling at different temperatures around the LCST. The solvent release through the hydrogel was modeled using a two-dimensional diffusion model with moving boundaries. In addition, the polymerization of ionic bigels was performed by using the molecular imprinting method in order to improve the loading capacity of these materials. Loading capacity of imprinted hydrogel samples (IH) were almost 50% higher for both analyzing analytes, than that of non-imprinted (NIH). At early stages of the project, poly(NIPAAm) hydrogel were investigated experimentally to find out the effect of temperature, pH, solvent concentration and solvent composition on the hydrogel behavior i.e. the swelling reversibility. The dimensional changes accompanied with the volume phase transition of the thermosensitive poly(NIPAAm) hydrogel based on changing the diffusion and equilibrium parameters were investigates closely. Moreover, characterizing the presented hydrogel using Raman spectroscopy was performed. The effect of the hydrogel shrinking process on the drug release has also been discussed. To achieve the goal of the research, two experimental setups were designed. The first (uniaxial compression apparatus) was designed to measure the viscoelastic properties of the cylindrical hydrogels as a function of its dimensions, swelling ratio, equilibrium temperature and diffused solvent. Besides, this uniaxial compression apparatus was used to successfully determine the collective diffusion coefficient, Dcol for the moving boundary thermosensitive poly(NIPAAm) hydrogels swelled to equilibrium in a solvent. From the uniaxial compression apparatus, collective diffusion coefficient was calculated using the correlation developed by Tanaka [Tanaka et. al., 1973]. Besides using Raman spectroscopy to investigate the hydrogel, it was used as a modern non-destructive method to determine the mutual diffusion coefficient (Dmut) in thermo-sensitive poly(NIPAAm) hydrogels. Part of this project was done in close cooperation with the University of Chemical Technology and Metallurgy, in Sofia, Bulgaria to develop a bi-dimensional diffusion model with moving boundary conditions describing the solvent release through the hydrogel.
Publications
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Raman Spectroscopy: Stimuli Responsive Hydrogels for Biomedical Applications. Chem. Eng. Tech. 80 (9) (2008) 1312
Naddaf A. und Bart H.-J.
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Swelling Characteristics of Poly(NIPAAm) Using Confocal Raman Microscopy. Proceedings of the 18TH International Congress of Chemical and Process Engineering, CHISA. Prague (Czech Republic), 24 th -28th August 2008
Naddaf A. and H.-J. Bart
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Diffusion Kinetics of BSA Protein in Stimuli Responsive Hydrogels. Defect and Diffusion Forum, 297-301 (2009) 664-669
Naddaf A. A., Tsibranska I. and Bart H.-J.
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Konfokale Raman Spektroskopie: Adsorptionskinetik in thermosensitiven Hydrogelen. Chem. Eng. Tech. 81 (8) (2009) 1080
Naddaf A. und Bart H.-J.
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Kinetics of BSA Release from Poly(N- isopropylacrylamide) Hydrogels. Chem. Eng. and Process. Process Intensification 49 (2010) 581-588
A. A. Naddaf, I. Tsibranska and H.-J. Bart
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Transportvorgänge in Hydrogelen Chem. Eng. Tech. 82 (9) (2010) 1377
Naddaf A. A. und Bart H.-J.
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Diffusion Kinetics in Thermosensitive Hydrogel. Macromolecules Symposia (2011)
Naddaf A. A. and Bart H.-J.
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Raman Spectroscopy: Mutual Diffusion Coefficient in Hydrogels. Defect Diffusion Forum, 312-315 (2011) 193-198
Naddaf A. A. and Bart H.-J.
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Thermosensitive Poly(NIPAAm) Hydrogel: Drug Release Kinetics. J. of Mater. Sci. and Eng. ISSN 1934-8959, USA, 5 (8) (2011)
Naddaf A. A. and Bart H.-J.
