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Analyse des Einflusses der Kettenlänge der Edukte und des Reaktionsfortschrittes einer Veresterungsreaktion auf das Quellverhalten stimuli-responsiver Gele am Beispiel von Poly-N-Isopropylacrylamid
Citation Link: https://doi.org/10.15480/882.4845
Publikationstyp
Bachelor Thesis
Date Issued
2022-12-13
Sprache
German
Author(s)
Referee
Title Granting Institution
Technische Universität Hamburg
Place of Title Granting Institution
Hamburg
Examination Date
2022-12-23
Institut
TORE-DOI
Citation
Technische Universität Hamburg (2022)
A special ability of stimuli-responsive gels is the reversible solvent uptake in response to the influence of external stimuli, which has great potential for technical applications. However, this behaviour has not yet been researched. To achieve a better understanding of the chemo-responsive behaviour of gels, the swelling behaviour of poly-N-isopropylacrylamide (PNIPAAm) in different solvents and solvent compositions was investigated in this work.
For this purpose, the swelling behaviour of PNIPAAm in various pure substances of the substance classes of carboxylic acids, alcohols and esters was first considered. It was found that hydrophilic and polar properties of the solvents cause positive swelling behaviour, while hydrophobic properties have a negative effect on the swelling behaviour.
In addition, the swelling behaviour was investigated as a function of the reaction progress in various esterification reactions. High degrees of swelling were obtained up to high conversions, followed by a sharp decrease at complete conversion, indicating a dominant influence of the polar solvents. It was also recognised that with increasing length of the acid residue or alcohol residue, the influence of the other residue on the swelling behaviour decreased.
Furthermore, it must be considered that the thermodynamic swelling equilibrium is superimposed by the swelling kinetics. This is noticeable from the molecular sizes. As the chain length of the residues increases, it can be assumed that the esters diffuse out of or into the gel matrix more slowly, which could lead to the reaction mixtures with short-chain esters showing an increase in the degree of swelling at high conversion rates.
For this purpose, the swelling behaviour of PNIPAAm in various pure substances of the substance classes of carboxylic acids, alcohols and esters was first considered. It was found that hydrophilic and polar properties of the solvents cause positive swelling behaviour, while hydrophobic properties have a negative effect on the swelling behaviour.
In addition, the swelling behaviour was investigated as a function of the reaction progress in various esterification reactions. High degrees of swelling were obtained up to high conversions, followed by a sharp decrease at complete conversion, indicating a dominant influence of the polar solvents. It was also recognised that with increasing length of the acid residue or alcohol residue, the influence of the other residue on the swelling behaviour decreased.
Furthermore, it must be considered that the thermodynamic swelling equilibrium is superimposed by the swelling kinetics. This is noticeable from the molecular sizes. As the chain length of the residues increases, it can be assumed that the esters diffuse out of or into the gel matrix more slowly, which could lead to the reaction mixtures with short-chain esters showing an increase in the degree of swelling at high conversion rates.
DDC Class
500: Naturwissenschaften
540: Chemie
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