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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Multiscale Transport and Dynamics in Ion-Dense Organic Electrolytes and Copolymer Micelles

Kidd, Bryce Edwin 23 September 2016 (has links)
Understanding molecular and ion dynamics in soft materials used for fuel cell, battery, and drug delivery vehicle applications on multiple time and length scales provides critical information for the development of next generation materials. In this dissertation, new insights into transport and kinetic processes such as diffusion coefficients, translational activation energies (Ea), and rate constants for molecular exchange, as well as how these processes depend on material chemistry and morphology are shown. This dissertation also aims to serve as a guide for material scientists wanting to expand their research capabilities via nuclear magnetic resonance (NMR) techniques. By employing variable temperature pulsed-field-gradient (PFG) NMR diffusometry, which can probe molecular transport over nm – μm length scales, I first explore transport and morphology on a series of ion-conducting materials: an organic ionic plastic crystal, a proton-exchange membrane, and a polymer-gel electrolyte. These studies show the dependencies of small molecule and ion transport on modulations to material parameters, including thermal or magnetic treatment, water content, and/or crosslink density. I discuss the fundamental significance of the length scale over which translational Ea reports on these systems (~ 1 nm) and the resulting implications for using the Arrhenius equation parameters to understand and rationally design new ion-conductors. Next, I describe how NMR spectroscopy can be utilized to investigate the effect of loading a small molecule into the core of a spherical block copolymer micelle (to mimic, e.g., drug loading) on the hydrodynamic radius (rH) and polymer chain dynamics. In particular, I present spin-lattice relaxation (T1) results that directly measure single chain exchange rate kexch between micelles and diffusion results that inform on the unimer exchange mechanism. These convenient NMR methods thus offer an economical alternative (or complement) to time-resolved small angle neutron scattering (TR-SANS). / Ph. D. / Lithium ion batteries, fuel cells, and drug-delivery vehicles each depend on a fundamental understanding of the interface between materials science and molecular dynamics. Optimization of such materials usually requires routine analysis through common polymer characterization techniques. The present dissertation highlights the usage of an uncommon analytical tool to the polymer science community, nuclear magnetic resonance (NMR); and how it gives unprecedented access in gauging material performance when subjected to judicious multiscale analysis. Chemical specificity, non-destructiveness, and the ability to study dynamics on multi-time and length scales are only a few of the many advantages of NMR offers over other polymer characterization techniques. Chapters 3, 4, 5, 6, and 7 investigate different classes of materials for their respective applications to better understand the aforementioned interface. These studies are intended to spark interest in new research areas while supplementing existing ones.

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