Regensburg 2007 – scientific programme
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DY: Fachverband Dynamik und Statistische Physik
DY 29: Soft matter
DY 29.6: Talk
Thursday, March 29, 2007, 15:15–15:30, H3
Quantifying Cation Transport in Polymer Electrolytes in Terms of Microscopic Properties — •Arijit Maitra1,2 and Andreas Heuer1 — 1Institute of Physical Chemistry, University of Muenster, Germany 48149 — 2NRW Graduate School of Chemistry, Muenster, Germany 48149
We present an analytical approach to relate the macroscopic cation dynamics in polymer electrolytes via three principal time scales which characterize the local modes of cation transport. These are: polymer/segmental relaxation, the motion of the cation along the chain and cation jump events between different chains. With the knowledge that cationic motion is coupled to the segmental dynamics of polymers and applying the concept of renewal process (from dynamic bond percolation model) we are able to express the cation diffusion constant in terms of these three time scales. For the description of polymer dynamics, depending on chain length, we invoke the Rouse model and the Reptation model. Our theory is complemented by all-atom molecular dynamics simulation of a model system comprising of poly(ethylene oxide) and lithium tetrafluoroborate. Apart from furnishing a complete picture (both quantitative and qualitative) of the variety of cation transport mechanisms through the combination of theory and simulation, we are able to explain the chain length (N) dependence of lithium diffusivity (D) over a large range of N. This is supported by experimental data. Specifically, we find that the plateau regime of D(N) for large N does not require the presence of polymer entanglements, as has been speculated in the literature.