Glass Transition and Relaxation Processes of Nanocomposite Polymer Electrolytes

This study focus on the effect of delta-Al2O3 nanofillers on the dc-conductivity, glass transition, and dielectric relaxations in the polymer electrolyte (PEO)(4):LiClO4. The results show that there are three dielectric relaxation processes, alpha, beta, and gamma, in the systems, although the structural alpha-relaxation is hidden in the strong conductivity contribution and could therefore not be directly observed. However, by comparing an enhanced dc-conductivity, by approximately 2 orders of magnitude with 4 wt % delta-Al2O3 added, with a decrease in calorimetric glass transition temperature, we are able to conclude that the dc-conductivity is directly coupled to the hidden alpha-relaxation, even in the presence of nanofillers (at least in the case of delta-Al2O3 nanofillers at concentrations up to 4 wt %). This filler induced speeding up of the segmental polymer dynamics, i.e., the alpha-relaxation, can be explained by the nonattractive nature of the polymer-filler interactions, which enhance the "free volume" and mobility of polymer segments in the vicinity of filler surfaces