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CPP: Chemische Physik und Polymerphysik

CPP 27: POSTER Polymer Physics and Materials

CPP 27.40: Poster

Donnerstag, 30. März 2006, 17:00–19:00, P2

Ion mobility in PMMA doped with small amounts of a Lithium salt — •P. Kohn, K. Schröter, and T. Thurn-Albrecht — Department of Physics, Martin Luther University, Hoher Weg 8, 06120 Halle, Germany

Normally NMR techniques are used to determine the mobilities of ions in polymer electrolytes (via determination of diffusion coefficients and use of the Einstein relation). We discuss Time Of Flight (TOF) measurements in an electric field and parallel plate geometry as an alternative method to determine mobilities of ions. In a first step the ions of opposite charge are forced to seperate and accumulate at the different electrodes by applying a constant voltage. As a consequence of a reversed voltage in the second step the ions migrate from one electrode to the other. The current measured during this process gives the transit time which is directly related to the mobilities of the charge carriers.

For an exemplary application we used this method to study ion mobility in polymethylmethacrylate (PMMA) doped with lithiumtrifluorosulfonate (LiCF₃SO₃). The measurements were complemented by dielectric spectroscopy in the frequency domain. While the TOF measurements give the mobilities, the frequency dependent dielectric measurements give the temperature and salt-concentration dependence of the ohmic conductivity of the electrolyte.