Ion Conduction and Polymer Dynamics of Poly(2-vinylpyridine) - Lithium Perchlorate Mixtures

Ion conduction and polymer dynamics of single phase mixtures of poly(2-vinylpyridine) (P2VPy) with 0.1 to 10 mol{\%} lithium perchlorate (LiClO$_{4})$ were investigated using broadband dielectric spectroscopy. Interpretation of the relaxation behavior was assisted by findings from wide-angle and small-angle X-ray scattering experiments, and other techniques. Five dielectric relaxations were observed: a local $\beta $ process in the glassy state, a segmental relaxation, a slow segmental process, an ion-mode relaxation, and electrode polarization. The local P2VPy relaxation was strongly suppressed with increasing LiClO$_{4}$ content arising from the formation of transient crosslinks, which lead to a subsequent decrease in the number of free pyridine groups, and/or a reduction in the local free volume in the presence of LiClO$_{4}$. Ion conduction at low LiClO$_{4}$ concentrations ($<$ 10 mol{\%}) is governed by the diffusion of anions through the matrix, which is strongly coupled with the segmental relaxation. At relatively high LiClO$_{4}$ concentration (10 mol{\%}), partial decoupling between ion motion and the segmental relaxation was observed, leading to increased conductivity.