Proton mobility in oligomer-bound proton solvents: imidazole immobilization via flexible spacers

A completely new approach for obtaining high proton conductivity in polymers based on proton solvating heterocycles covalently bound via flexible spacers is presented. Imidazole-terminated ethyleneoxide (EO) oligomers as model materials have been characterized with respect to their conductivity by ac impedance spectroscopy and with respect to 1H- and 19F-diffusion coefficients by pulsed magnetic field gradient-NMR (PFG-NMR). Comparison of conductivity and NMR diffusion coefficients of pure and acid doped materials shows ‘structure diffusion’ (intermolecular proton transfer and structural reorganization by hydrogen bond breaking and forming processes) to be the dominant conduction process, which gives rise to proton conductivities of up to 5×10−3 S cm−1 at 120°C in completely waterfree materials.