Atomic force microscopy investigations

Structure and dynamics of conjugated polymers by Atomic Force Microscopy

Contact person: PD Dr. rer. nat. Elmar Bonaccurso

The sub-100 nm morphology of those conjugated polymers that already found their way into electronic industry applications is known to heavily influence the electromechanical properties and the performance of those materials. These properties are charge injection, transport, recombination, trapping, and the phase behavior and mechanical robustness of the polymer blend. Of paramount importance is also the analysis of the stability of these properties over time. Electrical atomic force microscopy (E-AFM) is an ideal tool to measure simultaneously electronic properties, surface morphology, and mechanical properties of thin films of conjugated polymers. E-AFM techniques can be combined to obtain complementary information of the materials studied. We, e.g., can perform combined topography, Kelvin probe force microscopy (KPFM), and the recently presented scanning conductive torsion mode microscopy (SCTMM) studies on thin conducting polymer films.

By a combined topographical, KPFM, and SCTMM analysis on a model system made of gold nanoparticles embedded in a polystyrene matrix we could draw helpful conclusions for inferring the nanostructure and the electronic properties of a home-made conjugated polymer compound: Polypyrrole/polystyrene sulfonate (PPy/PSS)

KPFM and SCTMM images of PPy/PSS thin films: a) and b) height and potential images by KPFM; c) and d) height and current images by SCTMM, current bias ) -4.1 V, current sensitivity )10 pA/V. All images are scans of 250 × 250 nm. The current image was flattened without modifying the current data.

  • Sun L., Wang J.J., Butt H.-J., Bonaccurso E., Influence of Relative Humidity on the Nanoscopic Topography and the Dielectric Constant of Thin Films of PPy:PSS, Small, 7, 950 (2011)
  • Sun L., Wang J.J., Bonaccurso E.: Nanoelectronic Properties of a Model System and of a Conjugated Polymer: A Study by Kelvin Probe Force Microscopy and Scanning Conductive Torsion Mode Microscopy, Journal of Physical Chemistry C, 114, 7161 (2010)
  • Muehlebach A., Hafner A., Rime F., Mpoukouvalas K., Sun L., Wang J.J., Wegner G., Beierlein T., Synthesis of Polypyrrole-Coated Core/Shell Nanoparticles, CHIMIA, 64, 49 (2010)
  • Wang J., Sun L., Mpoukouvalas K., Fassbender B., Bonaccurso E., Brunklaus G., Muehlebach A., Rime F., Butt H.-J., Wegner G.: Facile Synthesis of Spherical Polyelectrolyte Brushes as Carriers for Conducting Polymers to be Used in Plastic Electronics, Macromolecular Chemistry & Physics, 210, 1504 (2009)
  • Wang J., Sun L., Mpoukouvalas K., Lienkamp K., Lieberwirth I., Fassbender B., Bonaccurso E., Brunklaus G., Muehlebach A., Beierlein T., Tilch R., Butt H.-J., Wegner G.: Construction of Redispersible Polypyrrole Core-Shell Nanoparticles for Application in Polymer Electronics, Advanced Materials, 21, 1137 (2009)