Dielectric relaxations and conduction mechanisms in polyether-clay composite polymer electrolytes under high carbon dioxide pressure

The composite material P(EO/EM)-Sa consisting of synthetic saponite (Sa) dispersed in poly[ethylene oxide-co-2-(2-methoxyethoxy)ethyl glycidyl ether] (P(EO/EM)) is studied by "in situ" measurements using broadband electrical spectroscopy (BES) under pressurized CO2 to characterize the dynamic behavior of conductivity and the dielectric relaxations of the ion host polymer matrix. It is revealed that there are three dielectric relaxation processes associated with: (I) the dipolar motions in the short oxyethylene side chains of P(EO/EM) (beta); and (II) the segmental motion of the main chains comprising the polyether components (alpha(fast), alpha(slow)). alpha(slow) is attributed to the slow alpha-relaxation of P(EO/EM) macromolecules, which is hindered by the strong coordination interactions with the ions. Two conduction processes are observed, sigma(DC) and sigma(ID), which are attributed, respectively, to the bulk conductivity and the interdomain conductivity. The temperature dependence of conductivity and relaxation processes reveals that alpha(fast) and alpha(slow) are strongly correlated with sigma(DC) and sigma(ID). The "in situ" BES measurements under pressurized CO2 indicate a fast decrease in sigma(DC) at the initial CO2 treatment time resulting from the decrease in the concentration of polyether-Mn+ complexes, which is driven by the CO2 permeation. The relaxation frequency (f(R)) of alpha(slow) at the initial CO2 treatment time increases and shows a steep rise with time with the same behavior of the alpha(fast) mode. It is demonstrated that the interactions between polyether chains of P(EO/EM) and cations in the polymer electrolyte layers embedded in Sa are probably weakened by the low permittivity of CO2 (epsilon = 1.08). Thus, the formation of ion pairs in the polymer electrolyte domains of P(EO/EM)-Sa occurs, with a corresponding reduction in the concentration of ion carriers.