Enhancing the colloidal stability of nanoparticles dispersions, in order to extend the utilization time without any loss of performance, is desired. Prior works have confirmed the electrosteric stabilization of colloidal particles by so-called “amino-quat-primer” polymers, hyperbranched poly(ethylenimine) polymers containing amino groups and quaternized groups. In this work, a systematic investigation on the factors influencing the polymer-particle-interactions was carried out. Hence, aqueous silica-nanoparticle-dispersions were polymer-functionalized; their dispersions stability was studied using turbidity analysis; and the particle surface charge was examined employing electrophoretic measurements. Five key factors influencing the polymer-particle-interaction were defined, including: the polymer-particle-ratio, the degree of polymerization and the degree of functionalization of the polymer, the dispersion pH and the salt concentration. Alternatingly occurring areas of stable, unstable and again stable dispersions with an increasing polymer-particle-ratio occurred due to a charge reversal of bare, negatively charged to polymer-covered, positively charged particles. An additional area of unstable dispersions at very high polymer concentrations was assumed to arise from depletion forces of non-adsorbed free polymer. Stable, positively charged, polymer-covered silica nanoparticles were obtained for optimized conditions regarding the five key factors. After the dispersion stability enhancement, the new amino-functionalized surface could be used for further modifications, e.g. to result in a compatibility with a polymer matrix to fabricate highly functional polymer / inorganic hybrid materials.
| Identifer | oai:union.ndltd.org:uni-osnabrueck.de/oai:repositorium.ub.uni-osnabrueck.de:urn:nbn:de:gbv:700-2015111013669 |
| Date | 10 November 2015 |
| Creators | Brandt, Miriam |
| Contributors | Prof. Dr. Uwe Beginn, Prof. Dr. Lorenz Walder |
| Source Sets | Universität Osnabrück |
| Language | English |
| Detected Language | English |
| Type | doc-type:doctoralThesis |
| Format | application/pdf, application/zip |
| Rights | Namensnennung-NichtKommerziell-KeineBearbeitung 3.0 Unported, http://creativecommons.org/licenses/by-nc-nd/3.0/ |
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