University of Connecticut |
Polymer Program SeminarBlends, Bricks and Pores: An Exploration of Ion Transport and Thin Film Architectures Friday, January 19, 2007 11:00 am , IMS Room 20 In this work, I combine electrochemistry and polymer science to investigate the fundamental properties of polymer thin films and how they behave as electrolytes in modern energy systems. I will present how the architecture and structure of a material can have a significant impact on the way ions move in an electrolyte. My work examines a broad scope of architectures: free-standing hydrogen bonded blends, layered polymer-clay nanocomposites, and micro- to nano-scale porous thin films – all of which conduct protons and lithium ions in their own unique manner. The layer-by-layer (LbL) technique, employing the alternate adsorption of oppositely charged moieties, is a powerful tool for fabricating ultra-thin solid-state electrolytes; however, little is known about the materials properties of LbL assemblies owing to the significant challenge of isolating LbL thin films for analysis. In the course of my research, I have developed techniques to isolate substantial areas and mass of LbL films for thermal and mechanical analysis. Combing our understanding of materials properties and electrochemical impedance spectroscopy lets us design and engineer new solid state materials for electrochemical energy systems. Differential scanning calorimetry, thermal gravimetric analysis, dynamic mechanical analysis and impedance spectroscopy were performed on hydrogen-bonded LbL systems of poly(ethylene oxide) and poly(acrylic acid). These films behaved as elastomeric blends with fast ion transport in the humid state. X-ray diffraction, grazing-incidence small angle X-ray scattering, scanning electron microscopy (SEM), atomic force microscopy (AFM) and impedance spectroscopy were performed on polymer-clay LbL assemblies; observed data indicate that these polymer-clay films are highly anisotropic where transport in one direction is highly favored over another. AFM, SEM, optical microscopy and impedance spectroscopy were used to study microporous LBL films of poly(ethylene imine) and poly(acrylic acid). The microporous architecture demonstrated the transport properties of a liquid trapped within a solid matrix. These three morphologies can ultimately be designed and engineered for use in electrochemical energy systesms such as fuel cells and lithium batteries.
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