Leipzig 1999 – scientific programme

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PO: Polymerphysik

PO 13: Spektroskopische Methoden

PO 13.3: Talk

Tuesday, March 2, 1999, 16:40–17:00, HS 19

Dielectric analysis of ion conduction and the dynamics of Li+/O complexes in polymer electrolytes based on poly(ether-esters) and ethylene glycol substituted polysilanes. — •M. W"ubbenhorst¹, T.J. Cleij², L.W. Jenneskens², and J. van Turnhout¹ — ¹Department of Polymer Science and Technology, Technical University Delft, Julianalaan 136, 2628 BL Delft, The Netherlands — ²Debye Institute, Department of Physical Organic Chemistry, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands

Amorphous polymers containing ethylene glycol units show excellent solvation properties for Li+ ions. Such Li+/polymer complexes give rise to a high ion conduction. In this dielectric study, the temperature dependence of the ionic conductivity s will be related to the cooperative dynamics of the polymer backbones (a-process) and the Li+/polymer complexes ("chemical" a*-relaxation). Since the coordination of Li+ with ethylene glycol units establishes temporary crosslinks, the polymer dynamics shows enhanced cooperativity due to the increasing intermolecular interactions at higher salt concentrations. This is manifested in two ways: 1st the a-relaxation peak broadens and 2nd the apparent activation energy of the relaxation time ta and of s decreases for higher Li+ concentrations. At temperatures near and well above Tg, s does not obey a VFT-behaviour. This points to a split in the rotational and translational diffusion close to Tg, whereas at high temperatures the lost in cooperativity results in an Arrhenius behaviour.