Decoupling Ionic Conductivity from Structural Relaxation: A Way to Solid Polymer Electrolytes?

Using broadband dielectric spectroscopy, we studied the temperature dependence of ionic conductivity and structural relaxation in a number of polymers. We demonstrate that temperature dependence of ionic conductivity can be decoupled from structural relaxation in a material specific way. We show that the strength of the decoupling correlates with the steepness of the temperature dependence of structural relaxation in the polymer, i.e., with its fragility. We ascribe the observed result to stronger frustration in chain packing characteristic for more fragile polymers. We speculate that employment of more fragile polymers might lead to design of polymers with higher ionic conductivity.