Berlin 2001 – scientific programme

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CPP: Chemische Physik und Polymerphysik

CPP 7: Dynamics of Molecular Systems

CPP 7.4: Talk

Tuesday, April 3, 2001, 17:45–18:05, 112

Effective Size and Charge of Polyelectrolytes Determined by Dynamic NMR — •Ulrich Scheler and Shan Wong — Institute for Polymer Research Dresden, Hohe Strasse 6, D-01069 Dresden

Polyelectrolytes are polymers which contain charges on the polymer chain. Their properties are determined both by polymer properties like degree of polymerization and by electrostatic properties The effective size of the polyelectrolyte described by the hydrodynamic radius can be deduced from self-diffusion measurements using the Stokes-Einstein equation, which also yield the friction coefficient for the translation of the molecule. The effective charge of a molecule can be determined from the electrophoretic mobility provided the friction coefficient is known. A versatile method to probe dynamic displacements is pulsed field-gradient nuclear magnetic resonance (PFG-NMR), in which incoherent motion like diffusion and coherent motion like flow can be distinguished. Shielding of polyelectrolyte charges is manifested in decreasing hydrodynamic radius upon the addition of low molecular weight salt. A reduced electrophoretic mobility confirms a smaller effective polyelectrolyte charge.