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Understanding transport of water molecules and salt ions from a molecular level up to macroscopic length scales is critical to the design of novel materials for many applications, including separations membranes for fuel cell and desalination applications, as well as rechargeable battery technology. This work aims to investigate and develop new models correlating the dynamics and structure of polymeric materials, to the transport of small molecules within them, using a variety of Nuclear Magnetic Resonance (NMR) techniques. We present three studies through which we utilize two chemically similar membranes: hydroxyethyl acrylate-co-ethyl acrylate (HEA-co-EA) and hydroxymethyl methacrylate-co-methyl methacrylate (HEMA-co-MMA), which greatly differ in glass transition temperature, in order to understand the fundamental relationships from polymer chain dynamics and small molecule diffusion. From observations of the micron scale diffusion of these materials we find that the more dynamic, rubbery HEA-co-EA exhibits lower water to salt selectivity than HEMA-co-MMA, and that this difference arises from nanoscale morphology of the materials. From this, we propose a new model for hydrophilic pathways inside polymeric materials consisting of nanometer scale interconnected pathways are interrupted by micron scale arrangements of so-called "dead ends". We also for the first time show the separation of material tortuosity into two regimes, ranging from the nanometer-bulk and micron-bulk length scales. We further separate the contributions of structure from chemical interactions in the chemically similar desalination materials by investigating the local activation energy of diffusion in both materials, as well as aqueous solutions of the hydrophilic monomers analogous to the internal membrane environment. We find that the effects of local geometric confinement are very similar between the two materials, however the intermolecular interactions between water and the hydrophilic monomers, with respect to water transport, are significantly different between the two hydrophilic species. Geometric confinement accounts for a 5 ± 1 kJ/mol increase in diffusive activation energy from solution to membrane for both chemistries, and a 4 ± 1 kJ/mol difference in activation energy is seen between the two chemistries in both solution and membrane form. We propose that the entropic contributions to transport, are strongly impacted by the rigid environment of the HEMA material, and is related to the increased water-salt selectivity, as well as the increasing selectivity with increased ionic size observed compared to the HEA system. Using Dynamic NMR spectroscopy, we further investigate the differences seen in water-monomer intermolecular proton exchange by NMR. We utilize an iterative least-squares solving method to fit our exchange lineshape to a model of an uncoupled, two-site exchange lineshape in order to obtain rate and equilibrium population data from -50 to 70 °C. We find that, similar to the diffusive activation energy, the HEA-water system shows reduced enthalpy and entropy of the transition state compared to HEMA-water, such that there is faster exchange between HEMA and water at all temperatures measured, in addition to more biased populations in the HEA-water system. / Doctor of Philosophy / Understanding transport of water molecules and salt ions from a molecular level up to macroscopic length scales is critical to the design of novel materials for many applications, including separations membranes for fuel cell and desalination applications, as well as rechargeable battery technology. This work aims to investigate and develop new models correlating the dynamics and structure of polymeric materials, to the transport of small molecules within them, using a variety of Nuclear Magnetic Resonance (NMR) techniques. We will present three studies in which we seek to further understand the relationships between a material's physical and chemical properties, with the behavior of small molecules like water absorbed within the material. NMR spectroscopy, while not the standard method for characterizing desalination membranes, allows us to specifically probe direct effects on molecular motion of polymer structure from the microscopic level to the bulk, a feat not easily achieved by any other single technique. The first study presented within focuses on the differences in micrometer scale structure in two near identical sets of materials; differing only in that one is rubbery with flexible polymer chains, and the other is rigid with relatively immobile polymer chains. The second study takes these two materials and investigates them through a different lens, probing the molecular scale differences in water motions imparted by the flexible versus rigid polymer chains. The third and final study looks into the fundamental differences seen in how the two chemistries used to create the polymers in the first two studies interact with water molecules through a different NMR technique. These three studies together represent a series of methods and techniques that can be applied to many other classes of polymer materials, such as those destined for use in fuel cells and rechargeable batteries, in order to better understand the fundamental forces at work in those systems to aid in the design of the next generation's materials.

This research aimed to develop new composite membranes using a polymer of intrinsic microporosity (PIM-1) and metal organic frameworks (MOFs) for use in gas separations. PIM-1 was successfully synthesised using the high temperature method (40 min, 160 oC) and the resulting polymer was cast into membranes. PIM-1 membranes were chemically modified by reacting hexamethylenediamine (HMDA) with the nitrile group of PIM-1 to form HMDA-modified PIM-1 membranes. Surfaces of PIM-1 membranes were also modified by basic hydrolysis to form amide-modified PIM-1 membranes. These polymer materials were characterized by different techniques (GPC, NMR, ATR-IR, TGA, Elemental analysis and nitrogen sorption analysis). In addition, eight MOF materials [MIL-101(Cr), ED-g-MIL-101(Cr), TEPA-g-MIL-101(Cr), MIL-101(Cr)-NH2, MIL-101(Al)-NH2, UiO-66(Zr), UiO-66-NH2 and UiO-66(COOH)2] were successfully synthesized. They were chosen due to having high surface areas and large porosity. These MOF compounds were characterized using PXRD, SEM, TGA, and low pressure N2.Successful PIM-1/MOF MMMs were fabricated utilising PIM-1 and the MOFs outlined above with various loadings. The highest MOF loading achieved was 28.6 wt. %, apart from MIL-101(Cr)-NH2, for which it was 23.1 wt. %, and MIL-101(Al)-NH2, for which it was 19.8 wt. %. The morphology of MMMs was characterized by scanning electron microscopy (SEM), proving the dispersion of MOF fillers. Novel PIM-1 supported MOF membranes were successfully prepared by depositing ZIF-8 and HKUST-1 layers on the surfaces of unmodified and modified PIM-1 membranes. These materials were characterized using PXRD, SEM, ATR-IR and SEM-EDX. Gas permeation properties of the MOF/PIM-1 MMMs and PIM-1 supported MOF membranes were determined using a time lag method. Most MMMs tested showed an increase in the permeability and stable selectivity as the MOF amount was increased. However, this was not true for MIL-101(Al)-NH2, where the permeability and selectivity decreased. In contrast, PIM-1 supported ZIF-8 and HKUST-1 membranes caused a sharp decrease in the permeability and increase in the selectivity.

Mixed matrix nanocomposite membranes composed of a crosslinkable polyimide matrix and high-silica molecular sieve particles were developed for purifying natural gas. It was shown that ideal mixed matrix effects were not possible without sieve surface modification. A previously developed Grignard procedure was utilized to deposit magnesium hydroxide nanostructures on the sieve surface in order to enhance polymer adhesion. Analyses of Grignard-treated sieves pointed to the formation of non-selective voids within the surface deposited layer. These voids were suspected to lead to lower-than-expected membrane performance. In order to improve membrane transport, a reactive sizing procedure was developed to fill these voids with polyimide-miscible material. In a serendipitous discovery, as-received sieves--when treated with this reactive sizing procedure--resulted in nearly identical membrane performance as reactive-sized, Grignard-treated sieves. This observation lead to the speculation of a non-ideal transport mechanism in mixed matrix membranes.

In this study, we introduce novel, truly non-ionic hydrogen-bonded layer-by-layer (LbL) coatings for cell surface engineering capable of long-term support of cell function. Utilizing the LbL technique imparts the ability to tailor membrane permeability, which is of particular importance for encapsulation of living cells as cell viability critically depends on the diffusion of nutrients through the artificial polymer membrane. Ultrathin, permeable polymer membranes are constructed on living cells without a cationic pre-layer, which is usually employed to increase the stability of LbL coatings. In the absence of the cytotoxic PEI pre-layer, viability of encapsulated cells drastically increases to 94%, as compared to 20-50% in electrostatically-bonded shells. Engineering surfaces of living cells with natural or synthetic compounds can mediate intercellular communication, render the cells less sensitive to environmental changes, and provide a protective barrier from hostile agents. Surface engineered cells show great potential for biomedical applications, including biomimetics, biosensing, enhancing biocompatibility of implantable materials, and may represent an important step toward construction of an artificial cell.

The goal is of this project was to identify principles to guide the development of high performance dense film membranes for natural gas sweetening using hydrogen sulfide and carbon dioxide gas mixtures as models under aggressive sour gas feed conditions. To achieve this goal, three objectives were developed to guide this research. The first objective was to study the performance of cellulose acetate (CA) and an advanced crosslinkable polyimide (PDMC) dense film membrane for H₂S separation from natural gas. The second objective was to engineer those polymers to produce membrane materials with superior performance as measured by efficiency, productivity, and plasticization resistance, and the third objective was to determine the separation performance of these engineered membrane materials under more aggressive, realistic natural gas feeds, and to perform a detailed transport analysis of the factors that impact their performance. Work on the first objective showed that in neat CA, penetrant transport is controlled by both the solubility and mobility selectivity, with the former being more dominant, leading to a high overall CO₂/CH₄ (33) and H₂S/CH₄ (35) ideal selectivities. However, in uncrosslinked PDMC, H₂S/CH₄ selectivity favored sorption only, whereas CO₂/CH₄ selectivity favored both mobility and sorption selectivity, leading to a high CO₂/CH₄ (37) but low H₂S/CH₄ (12) ideal selectivities. However, the latter polymer showed more plasticization resistance for CO₂. In the second objective, both materials were engineered. A new technique referred to as “GCV-Modification” was introduced in which cellulose acetate was grafted using vinyltrimethoxysilane (VTMS), then hydrolyzed and condensed to form a polymer network. PDMC was also covalently crosslinked to enhance its performance. GCV-Modified CA showed significant performance improvements for H₂S and CO₂ removal; the permeability of CO₂ and H₂S were found to be 139 and 165 Barrer, respectively, which represented a 30X and 34X increase compared to the pristine CA polymer. The H₂S/CH₄ and CO₂/CH₄ ideal selectivities were found to be 39 and 33, respectively. Crosslinked PDMC showed a higher CO₂/CH₄ selectivity of 38 with a better plasticization resistance for CO₂ and H₂S. In the third objective, these materials were tested under aggressive ternary mixtures of H₂S/CO₂/CH₄ with both vacuum and nonvacuum downstream. Even under aggressive feed conditions, GCV-Modified CA showed better performance vs. PDMC, and it remained were fairly stable, making it a potential candidate for aggressive sour gas separations, not only because of its significantly higher productivity, which will help decrease the surface area needed for separation, thereby reducing operating costs, but also because of the lower cost of the raw material GCV-Modified CA compared to PDMC.

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Ion sensitive field effect transistors (ISFETs) are semiconductor sensors that have the capability to determine the selected concentration of a specific ion in a solution. Most modern ISFETs utilize their ion selective properties for glucose monitors for diabetics. However, in this thesis, the ISFET fabricated is for the selective detection of K+. The goals of this thesis are to develop a functioning ion-selective polymer membrane, manufacture a working FET device, and implement the two aspects together into a working bench-top K+ selective ISFET device. Properties of a polymer composed of 33 wt.% polyvinyl chloride (PVC) 66 wt.% dioctyl sebacate (DOS) and 1 wt.% valinomycin applied to an ion-sensitive electrode (ISE) were investigated. The membrane generated a sensitivity value of -9.864E-08 Ω/log10(CK). Though this data set was affected by both the maximum resolution of the I-V curve tracing device and the thin-membrane effect. Selectivity tests following the IUPAC two-solution method in the presence of Na+ as the interfering ion, provided selectivity values of 0.228 and 0.443 with higher ratios of primary ion to interfering ion resulting in higher selectivity coefficients. Additionally, utilizing an illumination test, dielectric constants of 17.71 and 10.88 were calculated dependent on the amount of solvent used during formulation. Fabrication of the FET device also resulted in developments in metal contact materials, nitride film processing, and physical vapor deposition (PVD) processes. With further improvements, it is possible to fabricate a biocompatible, wearable K+-selective monitor for continuously testing dialysis patients.

Eine spezielle Art poröser Membranen sind die sogenannten Mikrosiebe. Ihre Dicke ist geringer als der Durchmesser der Poren und sie besitzen eine einheitliche Porengröße und eine dichte Porenpackung. Sie zeichnen sich somit durch eine hohe Trennschärfe aus und eignen sich daher und aufgrund ihres geringen Filtrationswiderstandes besonders für den Einsatz als Filtrationsmedien. Ein Prinzip, um Mikrosiebe herzustellen, ist die Partikel-assistierte Benetzung. Bei dieser Methode wird ein polymerisierbares organisches Öl zusammen mit Kieselgelpartikeln auf einer Wasseroberfläche gespreitet. Nach dem Auspolymerisieren des Öls und dem anschließenden Entfernen der Partikel erhält man die gewünschten Mikrosiebe, welche an den Stellen, an denen sich zuvor die Kieselgelpartikel befanden, Poren besitzen. Die Porengröße der Siebe ist dabei über die Größe der verwendeten Partikel in weiten Grenzen (ca. zwischen 20 nm und 1000 nm) einstellbar und die Größe und Form des Mikrosiebes wird lediglich durch die Flächengröße und -form der zur Herstellung verwendeten Wasseroberfläche vorgegeben. Jedoch ist die mechanische Stabilität der Mikrosiebe für die gewünschte Anwendung als Filtrationsmedium oftmals nicht zufriedenstellend. Daher ist eine Stabilisierung erforderlich. Eine Möglichkeit, diese Stabilisierung zu erreichen, ist das Aufbringen einer externen makroporösen Stützstruktur. Im Rahmen dieser Arbeit wird die Möglichkeit vorgestellt mittels der Drucktechnik des sog. Inkjet-Druckens eine potentielle Stützstruktur auf ein solches Mikrosieb zu applizieren und dieses somit zu stabilisieren.