Effect of Polymer Topology on Microstructure, Dynamics, Rheology, and Ionic conductivity in PEO based electrolytes

Microstructure, dynamics, and ionic conductivity of neat linear polymers have been extensively studied for solid polymer electrolytes in the past. In this work, we used poly (ethylene oxide) of various architectures (linear, stars and hyper-branched) and lithium contents to explore the effects of chain topology and molar ratio of the salt on glass transition, crystallization, mechanical properties, and ionic conductivity of PEO based electrolytes. XRD results suggest that room temperature crystallinity is suppressed more for the non-linear PEOs compared to the linear chains due to high degree of branching and completely diminished with lithium content exceeding 0.08 (Li/EO ratio) for all PEO topologies. Independent of polymer architecture, DSC results showed increase in T_g values that is similar in all electrolytes, suggesting a similar slowing down of alpha relaxation. Electrochemical impedance spectroscopy results indicate that the ionic conductivity in electrolytes with non-linear PEO topologies is higher than their linear analogues. Finally, the rheology of the electrolytes shows a decrease in the viscosity when non-linear PEO architectures are employed in comparison to the linear PEO.