Low frequency dielectric relaxation processes and ionic conductivity of montmorillonite clay nanoparticles colloidal suspension in poly(vinyl pyrrolidone)−ethylene glycol blends

Abstract

The dielectric dispersion behaviour of montmorillonite (MMT) clay nanoparticles colloidal suspension in poly(vinyl pyrrolidone)-ethylene glycol (PVP-EG) blends were investigated over the frequency range 20 Hz to 1 MHz at 30°C. The 0, 1, 2, 3, 5 and 10 wt% MMT clay concentration of the weight of total solute (MMT+PVP) were prepared in PVP-EG blends using EG as solvent. The complex relative dielectric function, alternating current (ac) electrical conductiv- ity, electric modulus and impedance spectra of these materials show the relaxation processes corresponding to the micro- Brownian motion of PVP chain, ion conduction and electrode polarization phenomena. The real part of ac conductivity spectra of these materials obeys Jonscher power law σ'(ω )= σdc + Aω n in upper frequency end of the measurement, whereas dispersion in lower frequency end confirms the presence of electrode polarization effect. It was observed that the increase of clay concentration in the PVP-EG blends significantly increases the ac conductivity values, and simultaneously reduces the ionic conductivity relaxation time and electric double layer relaxation time, which suggests that PVP segmen- tal dynamics and ionic motion are strongly coupled. The intercalation of EG structures in clay galleries and exfoliation of clay sheets by adsorption of PVP-EG structures on clay surfaces are discussed by considering the hydrogen bonding inter- actions between the hydroxyl group (-OH) of EG molecules, carbonyl group (C=O) of PVP monomer units, and the hydroxylated aluminate surfaces of the MMT clay particles. Results suggest that the colloidal suspension of MMT clay nano particles in the PVP-EG blends provide a convenient way to obtain an electrolyte solution with tailored electrical con- duction properties.