Thermal Behavior and Ion Conductivity of Polyethylene Oxide/Polyhedral Oligomeric Silsesquioxane Nanocomposite Electrolytes

We prepared and characterized nanocomposites of polyethylene oxide (PEO)/polyethylene glycol-polyhedral oligomeric silsesquioxane (PEG-POSS), all of which incorporated a KI/I-2 salt system, as electrolytes. Differential scanning calorimetry was used to investigate their melting and crystallization behaviors and to measure their respective degrees of crystallinity over mixing wide range of compositions. The degree of crystallinity reduced with POSS content, indicating restricted segmental motion of the polymer chains. Morphological observations were made using a polarized microscope, and the spherulite patterns observed in PEO/KI/I-2 collapsed with added POSS. A decrease in storage modulus was also observed by dynamic mechanical analysis. The ion conductivity measured by electrochemical impedance spectroscopy was enhanced from 1.19 x 10(-5) to 1.27 x 10(-4) S<bold>cm(</bold>-1) at 70wt% POSS; presumably, this was due to the combined effects of lower crystallinity, lower glass transition, and lower modulus as POSS content increases.