Master of Science in Engineering (MSE)
This dissertation describes advanced metrology and molecular dynamics simulations for quantifying counterion condensation in block copolymer electrolyte thin films. The fraction of condensed counterions (fc) were quantified in nanostructured block copolymer electrolyte (BCE) and random copolymer electrolyte (RCE) thin films with new and established experimental techniques. The transition between the osmotic-controlled regime and condensation-controlled regime in BCEs and RCEs was identified using solution uptake measurements via a quartz crystal microbalance (QCM) and environmental grazing incidence small-angle x-ray scattering (GI-SAXS). The activity coefficients of ions in thin film were quantified experimentally and these values matched predictions from Manning’s Theory of counterion condensation if the average distance between fixed charges on the polymer chains were determined accurately. Experimental results were compared against theoretical predictions from Manning’s Theory and molecular dynamics simulations. Interestingly, ionic conductivity measurements of the BCE thin films with aqueous solutions and humidified vapor revealed that solvation is critical for breaking ion pairs, and that the notion of two distinct counterion types, condensed and non-condensed, may not be the most accurate picture despite the utility of Manning’s theory for accurately predicting the activity coefficient of ions in polymer electrolytes.
Lei, Qi, "Probing Counterion Condensation Phenomena in Nanostructured Thin Film Block Copolymer and Random Copolymer Electrolytes" (2020). LSU Doctoral Dissertations. 5334.
Christopher G. Arges