Dokument: Investigation of the pressure dependency of phase equilibria in colloidal model systems
| Titel: | Investigation of the pressure dependency of phase equilibria in colloidal model systems | |||||||
| Weiterer Titel: | Untersuchung der Druckabhaengigkeit von Phasengleichgewichten in kollodialen Modelsystemen | |||||||
| URL für Lesezeichen: | https://docserv.uni-duesseldorf.de/servlets/DocumentServlet?id=18646 | |||||||
| URN (NBN): | urn:nbn:de:hbz:061-20110713-120204-2 | |||||||
| Kollektion: | Dissertationen | |||||||
| Sprache: | Englisch | |||||||
| Dokumententyp: | Wissenschaftliche Abschlussarbeiten » Dissertation | |||||||
| Medientyp: | Text | |||||||
| Autor: | Tomczyk, Karolina [Autor] | |||||||
| Dateien: |
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| Stichwörter: | Pressure, model system | |||||||
| Dewey Dezimal-Klassifikation: | 500 Naturwissenschaften und Mathematik » 530 Physik | |||||||
| Beschreibung: | In this thesis the experimental studies of pressure jumps effect on several systems,
representing a cross-section of soft matter materials. The phase behaviour of colloidal dispersions and polymeric micellar solutions using temperature and pressure as variables are presented in the first part. The second part addresses the correlation between temperature dependency of polymer viscosity and the diffusion time of a nanoscopic probe dissolved in this polymer. As the first subject-matter, the interplay between percolation and phase separation effect appearing in an adhesive hard sphere (AHS) system, represented by octadecyl coated silica particles dissolved in toluene, is discussed. The transitions to the percolated and the biphasic states are obtained and they are in agreement with theoretical predictions. For concentrations higher than around 12-14vol%, the increase of the forward scattering intensity is found to be governed by the proximity of the spinodal line. But it is the percolation effect that controls the time scale at which the forward scattering intensity increases. For lower concentrations two approaches to determine spinodal line were proposed. Depending on the way of spinodal determination the system is expected to undergo phase separation either through nucleation or spinodal decomposition process. In the first scenario the sample starts to reveal the non-ergodic behaviour while forming nuclei (the denser phase), and the spinodal lies below the percolation line in the phase diagram. In the latter scenario the spinodal is expected to lie between binodal and percolation lines, and while system is decomposing, the sample volume spanning network is formed, which gives rise to non-ergodic behaviour attributed to the percolated state. This is the first study of competition between percolation and phase separation addressed with time-resolved measurement. In the next chapter the temperature- and pressure-dependent behaviour of the water and water-DMF solutions of polymeric micelles composed of poly(ethylene-copropylene- b-(ethylene oxide)) (PEP-PEO) block copolymer is described. It is found that the micellar radius of gyration for the water solution decreases while approaching the lower critical solution temperature (LCST), which is obtained by increasing temperature and pressure. However, in water-DMF dispersion there is no change in micellar radius 4 until the phase separation sets in. In the first case applying pressure has similar effect as increasing temperature (although there is no simple linear dP/dT relation), and in the latter case it acts as lowering of temperature. In the last part the temperature dependence of diffusion of rubrene in the poly(ethylene-co-propylene) (PEP) polymer melt is investigated by fluorescence correlation spectroscopy. Its correlation with temperature dependence of polymer viscosity is found. This is a proof that the changes in rubrene diffusion while varying temperature are solely due to temperature variation of PEP viscosity. | |||||||
| Lizenz: |  Urheberrechtsschutz | |||||||
| Fachbereich / Einrichtung: | Mathematisch- Naturwissenschaftliche Fakultät » WE Physik | |||||||
| Dokument erstellt am: | 13.07.2011 | |||||||
| Dateien geändert am: | 13.07.2011 | |||||||
| Promotionsantrag am: | 18.05.2011 | |||||||
| Datum der Promotion: | 29.06.2011 |
