Conductivity Mechanism in Polymerized Imidazolium-Based Protic Ionic Liquid [HSO₃–BVIm][OTf]: Dielectric Relaxation Studies

Abstract

In this paper, we investigate the molecular dynamics and ions transport properties of polymerized imidazolium-based protic ionic liquid [HSO3–BVIm][OTf]—a new material with potential applications in energy storage and electrochemical devices. The results of dielectric measurements, analyzed in modulus M*(f) and conductivity σ*(f) formalisms, combined with temperature-modulated differential scanning calorimetry experiments, have revealed a fundamental difference between the conducting properties of the examined polymer membrane and its low-molecular weight counterpart. Our findings indicated a strong decoupling between conductivity relaxation times τσ (related to the ions migration through the polymer matrix) and segmental dynamics when the ionic transport is controlled by fast proton hopping through the dense hydrogen-bond network. Finally, we also discuss, for the first time, the effect of water content on the glass transition temperature value, relation between the charge and mass diffusion, reflected in the decoupling phenomenon, and the conductivity mechanism of examined poly[HSO3–BVIm][OTf].