Dresden 2003 – wissenschaftliches Programm

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CPP: Chemische Physik und Polymerphysik

CPP 20: POSTER A

CPP 20.39: Poster

Montag, 24. März 2003, 19:00–21:00, ZEU/250

Effective Size and Charge of Polyelectrolytes — •Ulrich Scheler and Ute Böhme — Institute for Polymer Research Dresden, Hohe Str. 6, D-01069 Dresden

Electrostatic interactions dominate charge and conformational properties of polyelectrolytes in solution. Because of counterion condensation only a fraction of the nominal charge, is accessible for interaction with other molecules or solid surfaces [1]. Determination of effective charge and size is possible via PFG NMR [2]. From the diffusion coefficient the hydrodynamic size of the molecules is derived. Its molecular weight dependence yields the fractal dimension of the molecules, describing the use of space, which drastically increases with the ionic strength of the solution. This is explained by both, the screening of the polyelectrolyte charges and the forced counterion condensation [3]. The effective charge is determined from an combination of diffusion and electrophoresis NMR. While the diffusion provides the friction coefficient, electrophoresis provides the mobility, From both the effective charge can be calculated. The comparison with predicted values assuming an linear arrangement shows, that the experimentally acquired effective charge of polyelectrolytes is smaller, indicating stronger counterion condensation than expected [4]. 1 Manning, G.S., in ’Polyelectrolytes’, Sèlègny, E. et al. Eds., D. Reidel Publishing, , 1974. 2 U. Scheler in H.S. Nalva ’Handbook of Polyelectrolytes and their applications’, American Scientific Publishers (2002) 3 U. Böhme, U. Scheler, Macrom. Symp., 184, (2002), p. 349 4 U. Böhme, U. Scheler, Coll. Surf. A. ( in press)