COLL 228 |
| Liang Hong, Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, 104 S Goodwin, Urbana, IL 61801 and Steve Granick, Departments of Materials Science and Engineering, of Chemistry, of Physics, and of Chemical and Biomolecular Engineering, University of Illinois, 104 S Goodwin, Urbana, IL 61801. |
| The comprehensive understanding of polymer diffusion in nonpolar solvents is not matched yet by equal understanding of diffusion in charged systems and in heterogeneous environments. In the present experimental studies, we employ fluorescence correlation spectroscopy (FCS) with two photon excitation, taking advantage of the femtoliter focused volume and molecular sensitivity of this method. Experiments can thus be performed from extremes of dilute solution (ng/mL) to solutions so concentrated that they approach the glass transition. In this poster, poly-L-glutamic Acid, a weak polyelectrolyte with hydrophilic backbone, was selected as the model system, labeled at one terminus with a fluorescent probe. At pH=6.8, increase of diffusion coefficient was observed with concentration increasing significantly in the dilute region, followed by a sharp drop at higher concentration. An advantage of this experimental system is that it is possible to vary the polyelectrolyte charge density simply by varying the pH. The dependence on concentration, ionic strength and polyelectrolyte charge density is under continuing investigation. The peculiar effects of ion valence may be discussed; we find tentatively that dynamics are altered significantly in the presence of trivalent and tetravalent salts. |
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Posters: Fundamental Research in Surface and Colloid Chemistry
6:00 PM-8:00 PM, Monday, March 29, 2004 Disneyland -- North Exhibit Hall, Poster
Division of Colloid and Surface Chemistry |