Shudipto Konika Dishari
Date of this Version
Johnson, T. J. Nanoscale Mechanical and Electrochemical Studies of Emerging Applied Polymeric Systems, M.S. Thesis, University of Nebraska-Lincoln, 2020.
The nanoscale understanding of interfacial mechanical and ion-conduction behavior of polymeric systems is essential and also challenging because of the inherent difficulty with designing experiments that can work effectively at this lengthscale. Mechanical and electrochemical characterization of supported, ion-conducting polymer (ionomer) thin films < 1 µm thick is complicated by the presence and interactions of the films with their support. Additionally, nanoscale metrologies are critical for understanding the interaction mechanism at the interface of antimicrobial polymers and bacteria. Interpretation of results is also challenging, with considerations such as analytical and constitutive modeling based on linear viscoelasticity (mechanical) and equivalent circuit elements (electrochemical) used to interpret the measured material response. Furthermore, some emerging applied polymeric systems in energy and biomedical applications could significantly benefit from nanoscale characterization to help explain the material limitations in order to inform the design of more effective material solutions. The objective of this work was to develop a better understanding of the nanoscale material properties, interfacial phenomena, and interaction mechanisms of selected polymeric material systems using atomic force microscopy (AFM) and electrochemical impedance spectroscopy (EIS). First, thin films of ionomers for energy conversion/storage applications were investigated with AFM and EIS to understand the nature of ion-transport limitations and thin film confinement. Additionally, bio-based ionomer thin films were explored to demonstrate their suitability for electrochemical devices. The combination of AFM and EIS studies provided insights into the thin-film confinement phenomena. Secondly, model cationic-conjugated oligo/polyelectrolytes (CCOEs/CCPEs) were used to treat wild-type and antibiotic-resistant strains of Escherichia coli (E. coli), and the interactions of CCOE/CCPE with the bacteria were studied with AFM. The study helped to understand the action mechanism of conjugated molecules while exhibiting bacterial growth inhibition.
Advisor: Shudipto Konika Dishari