Dr. Uwe Lappan

Contact Dynamics in self-assembled polymer systems
at the Leibniz-Institut für Polymerforschung Dresden e.V.

Hohe Strasse 6
01069 Dresden

Phone: +49 (0)351 4658-366
Fax: +49 (0)351 4658-231
Email: lappan@ipfdd.de

We are using the EPR spin-label technique to study local dynamics in self-assembled polymer systems such as polyelectrolyte multilayers and polyelectrolyte complexes.

Electron paramagnetic resonance (EPR) is a spectroscopic technique for the study of structure and dynamics of paramagnetic species. Most polymeric materials, however, are diamagnetic and thus do not exhibit EPR signals. The absence of signals from the material provides the opportunity to apply EPR as a selective probe technique, whereby stable paramagnetic species such as nitroxide radicals are introduced. These radicals are called spin labels if they are covalently linked to the macromolecules. Rotational dynamics of the spin labels on time scales between 10 ps and 1 µs can be characterized by the fast and sensitive continuous wave EPR. The rotational dynamics of the spin labels is influenced by the restricted motion of the side group bearing the spin label and local polymer backbone motions at the point of the covalent linking of the spin label. Information about the dynamics is obtained by simulation and fitting the experimental spectra. We have demonstrated that rotational dynamics of polymer segments in polyelectrolyte complexes and multilayers can be investigated by spin-label EPR. In addition, polyion substitution and exchange reactions can be closely monitored by this technique.

• DFG: Investigations on the dynamics of polyelectrolyte multilayers by spin-labeling and EPR spectroscopy

• various topics and materials (PB1 and PB2)

• Naas, C.; Scheler, U.; Lappan, U., Influence of pH on the Growth and the Local Dynamics of Polyelectrolyte Multilayers. Macromolecules 2021, 54 (2), 1043-1051
  DOI: 10.1021/acs.macromol.0c01756.
• Lappan, U.; Scheler, U., Polyanion Substitution in Polyelectrolyte Complex Dispersions Studied by Spin-Label EPR Spectroscopy. Macromolecules 2019, 52 (19), 7218-7223
  DOI: 10.1021/acs.macromol.9b01611.
• Lappan, U.; Rau, C.; Naas, C.; Scheler, U., Odd–Even Effect on Rotational Dynamics of Spin-Labeled Polyacid Chain Segments in Polyelectrolyte Multilayers. Macromolecules 2019, 52 (6), 2384-2392
  DOI: 10.1021/acs.macromol.9b00101.
• Lappan, U.; Scheler, U. Influence of the Nature of the Ion Pairs on the Segmental Dynamics in Polyelectrolyte Complex Coacervate Phases. Macromolecules 2017, 50 (21), 8631-8636
  DOI: 10.1021/acs.macromol.7b01858.
• Lappan, U.; Wiesner, B.; Scheler, U. Segmental Dynamics of Poly(acrylic acid) in Polyelectrolyte Complex Coacervates Studied by Spin-Label EPR Spectroscopy. Macromolecules 2016, 49 (22), 8616-8621
  DOI: 10.1021/acs.macromol.6b01863.