The ionic transport mechanism and coupling between the ion conduction and segmental relaxation processes of PEO₂₀-LiCF₃SO₃ based ion conducting polymer clay composites

Abstract

A series of ion conducting polymer-clay composites has been prepared using a solution casting technique. Relaxation dynamics and the ionic transport mechanism are systematically studied employing broadband dielectric spectroscopy over a wide frequency and temperature range. Among different phenomenological and theoretical models for ion conduction in disordered ionic conductors, conductivity isotherm spectra are analysed using the modified Almond-West and random free energy barrier model. Conductivity scaling suggests that the ionic transport mechanism is independent of temperature, and a similar inference is also obtained using scaled electrical modulus spectra. DC conductivity along with conductivity and segmental relaxation time following the Vogel-Tammann-Fulcher relationship suggests coupling between the ionic transport and segmental relaxation processes. Electrical modulus and dielectric formalism are used to understand the conductivity and segmental relaxation processes, respectively. The presence of first and second universality in the ionic transport mechanism is discussed using the real part of conductivity spectra and dielectric loss spectra. The crossover between the first and second universality is explained using the Kramer-Krönig approach. The ion diffusion coefficient is investigated using Ratner's classical approach in combination with the modified Stokes-Einstein relationship to correlate the coupled nature of the ion conduction mechanism and polymer segmental motion.

Investigation of Dielectric Properties of Polyethylene-Clay Nanocomposites for Quantifying Nanofiller Dispersion

“…Numerous studies have shown that polymer chain groups in composite structures can be more easily orientated by thermal excitation due to the applied field effect, [28][29][30][31][32][33][34] suggesting that in LLDPE-PE-g-MA/clay nanocomposite, DC conductivity has a significant contribution in the low frequency region due to ionic motion while it is not the case in LLDPE-OxPE/clay nanocomposite. 35 The peaks in both samples observed to shift towards high frequency indicate that the clay was not homogeneously dispersed in the structure due to the effect of the compatibilizer (OxPE) and that different polarization mech-anisms were formed, confirming the results of the study conducted by Durmuş et al on the structural characterization of LLDPE-OxPE/clay composites. 20,21 Figures 7, 8 and 9 show the temperature-dependent changes in the dielectric constant of pure LLDPE, LLDPE-PE-g-MA/ clay and LLDPE-OxPE/clay nanocomposites, respectively, in the frequency range of 10 -1 -10 6 Hz.…”

“…Moreover, the proportional arrangement of charges in question indicates a pronounced polarization between surfaces. 29,32,[34][35][36] The shift of dielectric losses to the high frequency region with an increase in temperature suggests that the conductivity of LLDPE-PE-g-MA/clay nanocomposite is somewhat higher than that of the others.…”

Ionic and conformational mobility in poly(vinylidene fluoride)/ionic liquid blends: Dielectric and electrical conductivity behavior

“…The latter relaxation is ascribed to local mobility [45]. It can also be observed that the M'' spectra are asymmetric when the temperature increases and skewed towards for higher frequencies for all the doped samples, suggesting fast ionic motion [47].…”

Relationship of Giant Dielectric Constant and Ion Migration in CH3NH3PbI3 Single Crystal Using Dielectric Spectroscopy

“…The relaxation time τ 2 depends on the process of charge accumulation on the electrode polarization. For the high-frequency behavior of the ac conductivity, the modified Almond–West formalism was used with the following equation where σ dc , ω c , n , and m are the dc conductivity, a crossover frequency, and a power law exponent, respectively; the parameter A is weakly dependent on temperature. Based on eqs and , the complex conductivity in the whole frequency region can be expressed as …”