Berlin 2005 – wissenschaftliches Programm
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CPP: Chemische Physik und Polymerphysik
CPP 5: SYMPOSIUM: Dynamics of multi-component fluids POSTER
CPP 5.10: Poster
Freitag, 4. März 2005, 17:15–19:00, Poster TU D
Diffusion and encapsulation of dextran probe molecules in sub-micron polyelectrolyte capsule dispersions measured using PFG-NMR — •Monika Schönhoff1 and Thorsteinn Adalsteinsson1,2 — 1Institut für Physikalische Chemie, Westfälische Wilhelms-Universität Münster, D-48149 Münster — 2current address: Department of Chemistry, Mount Holyoke College, S. Hadley, MA 01075, U.S.A.
Pulsed field gradient NMR(PFG-NMR) is introduced to probe the distribution and dynamics of long dextran sugars in colloidal dispersions of sub micron hollow polymeric capsules. The capsules are prepared using the layer-by-layer (LBL) self assembly method of strong polyelectrolytes onto silica particles, followed by a dissolution of the silica core. The capsules are permeable for water and small ions, but large molecules, such as polydextran, are found to be in slow exchange between two sites, the capsule interior and the exterior. 1H spin-spin (T2) and spin-lattice (T1) relaxation times of the encapsulated dextran are estimated from combined diffusion-relaxation measurements. Both relaxation times are used to calculate the population of encapsulated dextran and to discuss the state of the encapsulated dextran. The NMR measurements here indicate that the dextran may preferentially select the capsule interior, resulting in an enriched dextran concentration inside the capsules. The encapsulated dextran appears to be in a liquid-like state rather than being immobilized on the capsule wall. [J. Phys. Chem. B, in press]