Sabine Ludwigs1

1, University of Stuttgart, Stuttgart, , Germany

The presentation will give an overview about current activities in my team on the manipulation of thin films of conducting polymers. This includes structural control on the molecular and mesoscopic scale by controlled polymerization techniques and by directed crystallization, e.g. with solvent vapor annealing. We are particularly interested in electronic and electrochemical devices which deal with chemical or electrochemical doping of the polymer films, such as thermoelectric devices, battery or actuator applications. Both p-type[1] and n-type polymers[2] are in the focus of research as well as measurements of electronic and ionic conductivity.
Coming from classical poly(3-hexythiophene) (P3HT)[1] we have for example synthesized regioregular polythiophenes which bear functional pendant moieties in the side chains. Triphenylamine pendant groups have shown high potential as crosslinking units in films.[3],[4] Both electrochemical and chemical crosslinking have been studied with in-situ spectroscopy. The approach to chemically crosslink and simultaneously dope polymer films is highlighted as new approach to stable solvent-resistant doped polymer films. Pending sulfonate or imidazolium ions in the side chains on the other hand impart the polythiophene polymers with ionic conductivity.[5] We have experimental evidence for mixed conductivity in these conjugated polyelectrolytes. Similar to P3HT the electronic conductivity can be tuned over a wide range from insulating to around 2 S/cm by external doping with strong electron acceptors. The ionic conductivity is shown to strongly depend on the degree of water uptake. Impedance spectroscopy under controlled water vapor atmospheres and temperature give insights in the ionic conductivity with maximum measured values of 10-2 S/cm.
[1] S. Ludwigs, Editor, P3HT-revisited Adv. Polym. Sci., Springer, Heidelberg (2014) & G.L. Schulz, S. Ludwigs, Adv. Funct. Mater. 27 (2017) 1603083.
[2] Y. Gross, D. Trefz, R. Tkachov, V. Untilova, M. Brinkmann, G.L. Schulz, S. Ludwigs, Macromolecules 50 (2017) 5353-5366. & K. Tremel, F.S.U. Fischer, N. Kayunkid, R. Di Pietro, R. Tkachov, A. Kiriy, D. Neher, S. Ludwigs, M. Brinkmann, Adv.Energy Mater. (2014) 1301659.
[3] O. Yurchenko, J. Heinze, S. Ludwigs, ChemPhysChem 11 (2010) 1637-1640.
[4] P. Reinold, K. Bruchlos, S. Ludwigs, Simultaneous doping and crosslinking of polythiophene films, (2017) under revision.
[5] R. Merkle, P. Gutbrod, P. Reinold, M. Katzmaier, R. Tkachov, J. Maier, S. Ludwigs, Polymer (2017) under revision.