Dresden 2014 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 51: Charged Soft Matter II

CPP 51.4: Vortrag

Donnerstag, 3. April 2014, 15:45–16:00, ZEU 118

Rotational Dynamics of Polyelectrolyte Chain Segments Studied by Spin-Label EPR Spectroscopy — •Uwe Lappan, Brigitte Wiesner, and Ulrich Scheler — Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Straße 6, 01069 Dresden, Germany

The complex coacervation of oppositely charged polyelectrolytes has been studied by EPR spectroscopy. The spin-label technique employs stable radicals which are covalently attached to diamagnetic macromolecules. Rotational dynamics of such spin labels on time scales between 10 ps and 1 μs can be characterized by basic and fast CW EPR spectroscopy. The dynamics of the spin labels is influenced by the restricted motion of the side group bearing the label and local polymer backbone motions at the point of the covalent attachment of the label. A spin-labeled poly(ethylene-alt-maleic acid) with less than 5 mol-% of spin-labeled repeat units has been prepared. The segmental rotational mobility of the spin-labeled polyanion and the internal rotation of the spin label have been determined simulating the line shapes of the experimental EPR spectra. The complex formation of this weak polyanion with the strong polycation poly(diallyldimethylammonium chloride) has been studied as a function of mixing ratio and pH of the solution. If the spin-labeled polyanion is the excess component, the spectrum of a slow-motion component is superimposed by the spectrum of a fast-motion component. In the opposite case, the spectra are dominated by a slow-motion component.