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Dissertation zugänglich unter
Synthesis and characterization of hybrid polymers as new functional coating materials
Synthese und Charakterisierung von Hybridpolymeren als neue funktionelle Beschichtungsmaterialien
Dokument 1.pdf (24.444 KB)
Théato, Patrick (Prof. Dr.)
Tag der mündlichen Prüfung:
Kurzfassung auf Englisch:
In the present thesis, the synthesis of hybrid polymers based on the efficient modification chemistry of poly(methylsilsesquioxanes)-poly(pentafluorophenylacrylate) is described, yielding various substrate surfaces with different properties, such as anti-fouling and thermo- or light-responsive behavior. For this purpose, the new hybrid polymers poly(methylsilsesquioxane)-poly(4-vinyl benzaldehyde) (PMSSQ-PStCHO) and light- and temperature-responsive polymers were synthesized.
First, it was demonstrated an effective two-step approach to integrate zwitterionic α-aminophosphonic acids onto substrate surfaces, which were shown to provide antifouling effects.
Thereafter, silicon surfaces were functionalized with poly(methylsilsesquioxane)-poly(4-vinyl benzaldehyde) in THF. Subsequently, α-aminophosphonates were introduced on surfaces via Kabachnik–Fields post-polymerization modification (sur-KFR), by employing various combinations of amines and dialkyl phosphonates. The successful Kabachnik-Fields reaction of aldehyde functionalized surfaces with amines and dialkyl phosphonates was proven by precise analysis of the obtained surfaces, which included infrared, energy-dispersive X-ray and X-ray photoelectron spectroscopy measurements, confirming a practically quantitative conversion of aldehydes without any detectable structural defects. After subsequent deprotection reaction of dialkyl phosphonates, the obtained zwitterionic surfaces were characterized by various techniques, such as infrared spectroscopy, contact angle measurements and surface energy measurements. Additionally, bacterial cell adhesion assays and blood adsorption assays were conducted to prove antifouling properties of the resulting films. It was found that the obtained zwitterionic-functionalized polymer substrates exhibited a low protein adsorption in PBS buffer and showed reduced adhesion properties against S. epidermidis cells.
Then, different methods to generate of temperature- and light-responsive coatings on the surfaces were investigated. Therefore, new thermo- and light-responsive copolymers were synthesized, that are derived from alkylamines, yielding a thermo-responsive behavior with an amino-spiropyran as the corresponding photochromic group. To prepare the temperature- and light responsive coatings, two complementary approaches were explored. In the first approach, the reactive hybrid polymer is modified prior to deposition on a surface. Alternatively, a reactive hybrid polymer coating is deposited on a surface and subsequently functionalized via a post-modification route yielding the respective responsive surfaces.
In the present thesis, was presented the synthesis of hybrid polymers is described based on the efficient modification chemistry of poly(methylsilsesquioxanes)-poly(penta-fluorophenylacrylate) yielding various substrate surfaces that exhibit a thermo- or light-responsive behavior. Furthermore, the reversible isomerization of spiropyran moieties in the copolymers, which was induced by irradiation with UV light, had an influence on the water wettability behavior. First, different temperature-responsive coatings were prepared by surface-modification reactions inside the capillary and the accessible temperature-controlled switching range of the contact angles was directly measured using water with different temperatures. The obtained values are comparable to the results obtained by the sessile drop method but the error range is much smaller, which allows a more accurate determination of the equilibrium contact angles. This convenient method of reactive coatings inside glass capillaries may find further application in searching for other poly(acrylamide)-based stimuli-responsive coatings which may not be limited to temperature or light as a stimulus.
The results of this work show the versatility and the high potential of inorganic-organic hybrid polymers which are suitable for the preparation of various applications in different areas of life, such as medicine, microbiology, microelectronics and many others.