Dresden 2017 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 68: Hydrogels and Microgels II

CPP 68.9: Talk

Friday, March 24, 2017, 12:30–12:45, ZEU 260

Segmental Dynamics of Spin-Labeled Poly(acrylic acid) in Polyelectrolyte Complex Coacervates Studied by CW 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 continuous wave (CW) EPR spectroscopy. The spin-label technique employs stable radicals which are covalently attached to 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. The dynamics of polyelectrolyte complexes (PECs) composed of poly(diallyldimethylammonium chloride) (PDADMAC) and poly(acrylic acid) (PAA) was studied in dependence on pH and temperature using a spin-labeled PAA as reporter molecule. All of the experimental spectra were well reproduced by simulations based on the microscopic order/macroscopic disorder (MOMD) model. It was found that the segmental mobility of the PAA in the PECs is nearly constant in the range of pH from 10 to 5 but decreases dramatically for pH values lower than 5. It has been confirmed that the dynamics in the PECs is strongly influenced by the degree of dissociation of the weak polyacid.