Equilibrium Phase Behavior of Ionomers

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Charge-containing polymers have received considerable attention for many decades, as these polymers combine the flexibility of polymer chains with electrochemical properties of the ions to provide a highly tunable, chemically and mechanically versatile class of materials. These materials have found use in energy conversion devices, high-density energy storage devices such as batteries, biomedical applications as drug delivery mechanisms, organic photovoltaic devices, and surface coatings, among many. An effort to fully utilize and optimize these materials has called forth the need to understand the equilibrium phase behavior of charge-containing polymers. However, despite the wealth of theoretical and experimental investigations, a complete and comprehensive understanding of electrostatics in charge-containing polymers remains elusive. This thesis is an attempt to add to the existing literature by considering multi-scale effects of Coulombic interactions. Specifically, we attempt to describe the phase behavior across multiple regimes of dielectric constants observed in experimental systems. This thesis opens with a backdrop of current research in the field of neutral polymer systems and ionomer systems (Chapter 1). The rest of the thesis is organized into two sections. First, a theoretical framework for describing multi-scale effects of ionomer blends is developed (Chapter 2). It is found that the ion-ion correlations, incorporated into Flory-Huggins theory via liquid state theory, can qualitatively change the mixing thermodynamics in simple binary blends on ionomers (Chapter 2). The phase diagram is extended to a more complicated ternary ionomer blends, where plasticizer and salt effects are taken into account (Chapter 3). Interfacial adsorption of the minority component is investigated and compared against classical Flory-Huggins type treatment. In Chapter 4, dielectric heterogeneity is taken into account, and we examine multiple regimes of electrostatic interactions, where a different driving force dominates each regime. In the short second section, an experimental confirmation of theoretical results is attempted by identifying a model experimental system and conducting preliminary investigation on the equilibrium phase behavior at an interface and in the bulk (Chapters 5 and 6)

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  • 05/13/2019
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