CANCELLED: Prof. Monika Schönhoff "Functional Polyelectrolyte Materials: Charge transport, pH-triggering and molecular encapsulation"

Polyelectrolyte multilayers prepared by Layer-by-Layer (LbL) self-assembly are, due to their inherently low thickness, interesting candidates for applications as ion conductors. With this motivation we are studying fundamental charge transport properties by impedance spectroscopy. The dc conductivity dependence shows a strong exponential dependence on humidity, while frequency-dependent spectra are governed by unique scaling laws in dependence on temperature and humidity. As charge carriers, protons have been identified [1]. On the other hand, in LbL films containing gold nanoparticles, the dominating conduction mechanism is electronic charge transport. Dependencies on relative humidity lead to the conclusion that electron transport occurs via the gold particles, involving tunneling processes between particles. The conductivity can be reversibly tuned by humidity via control of interparticle tunneling probabilities.

On the other hand, polyelectrolyte multilayers are soft and easily swellable in suitable solvent environment, which provides further functionalities, such as tunable molecular uptake and release, triggered by pH variation. We have previously shown that polyelectrolytes can exhibit exponential or linear growth behavior in dependence on the assembly pH [2]. In addition to that, post-assembly pH treatment can yield controlled release systems, which can be prepared not only in planar, but even in colloidal geometry. Furthermore, aiming at molecularly well- defined uptake and release, molecular imprinting systems have been prepared employing LbL films, where selective and reversible guest molecule uptake and release is demonstrated [3].

Finally, polyelectrolytes can act as functional materials in Li+ conducting electrolytes, where polymers in general serve to enhance mechanical stability, for example in polymer gel electrolytes consisting of polymer, Ionic Liquid and Li salt. Here, we present a polyelectrolyte with remarkable conduction properties already in the monomeric form, which can be in-situ polymerized and has beneficial properties for Li+ conduction in the gel electrolyte form [4].

[1] Akgöl, Y.; Cramer, C.; Hofmann, C.; Karatas, Y.; Wiemhöfer H.D.; Schönhoff, M. Macromolecules
2010, 43(17), 7282-7287.
[2] Bieker, P.; Schönhoff, M. Macromolecules 2010, 43(11), 5052-5059.
[3] Gauczinski, J.; Liu, Z.; Zhang, X.; Schönhoff, M. Langmuir 2010, 26(12), 10122-10128. Gauczinski,
J.; Liu, Z.; Zhang, X.; Schönhoff, M. Langmuir 2012, 28(9), 4267-4273.
[4] Jeremias, S.; Kunze, M.; Passerini, S.; Schönhoff, M. J. Phys. Chem. B 2013, 117, 10596-10602.