This thesis investigates the lithium-ion dynamics and structural changes in the novel cathode material LiFeV2O7 by solid-state NMR spectroscopy and density functional theory (DFT). With the escalating demand for high-performance lithium-ion batteries (LIBs), exploring cathode materials that can offer superior energy density, cycle stability, and safety is crucial. LiFeV2O7 presents a fascinating structure because it incorporates two transition metals capable of undergoing redox processes, a feature highly beneficial for lithium-ion batteries. The research employs advanced DFT calculations to predict the electronic structure and 7Li NMR shifts. These theoretical insights are essential for understanding how structural disorder influences NMR results and how the oxidation state of transition metal impacts the Fermi contact shift. Experimental techniques, including solid-state NMR spectroscopy and diffraction methods, are applied to study the lithium-ion exchange process and structural evolution during electrochemical cycling. Selective inversion NMR experiments were used to quantify the exchange rates relative to lithiation levels, and in combination with diffraction methods and DFT calculations, enabled the development of a structure model that elucidates the corresponding phase changes in the material. Moreover, the thesis discusses the impact of structural modifications on the lithium-ion dynamics within Li1.71FeV2O7, revealing a direct link between specific crystallographic changes and enhanced lithium mobility. The integration of DFT calculations with experimental observations provides a comprehensive understanding of the material's behavior, paving the way for improvements in cathode design. Overall, this research contributes significantly to the field of LIBs, offering novel insights into the complex interplay between structure, dynamics, and electrochemical performance in cathode materials. / Thesis / Doctor of Science (PhD) / This thesis explores the lithium-ion dynamics and structural changes in the new cathode material LiFeV2O7 using solid-state NMR spectroscopy and density functional theory (DFT). As the demand for high-performance lithium-ion batteries (LIBs) grows, discovering cathode materials with better energy density, stability, and safety becomes crucial. LiFeV2O7 is particularly interesting due to its structure, which includes two transition metals that undergo redox processes. This study combines advanced DFT calculations with experimental techniques to understand how structural disorder and the oxidation state of transition metals affect NMR results. Solid-state NMR spectroscopy and diffraction methods are used to examine lithium-ion exchange and structural changes during battery cycling. The research identifies how specific crystallographic changes enhance lithium mobility, providing insights that can improve cathode design. This comprehensive study contributes to the development of more efficient and stable LIBs by revealing the complex interplay between structure, dynamics, and electrochemical performance.

<div>Despite the abundant current applications for ionic hydrogels, much about the stimuli-responsive behavior of these materials remains poorly understood. Due to the soft nature of these materials, the number of traditional characterization methods which can be applied to these systems is limited. Many studies have been conducted to characterize bulk property responses of these materials, and experimental studies have been produced examining the distribution of free ions around single polyelectrolyte chains. However, little experimental work has been published in which molecular-scale interactions are elucidated in confined polyelectrolyte networks. Furthermore, the way in which responsive properties, other than bulk swelling capacity, scale with ionic fraction in mixed polyelectrolyte-non-polyelectrolyte hydrogel systems has not been thoroughly investigated.</div><div>The distribution and strength of polymer-counter-ion bonds has a remarkable effect on hydrogel properties such as absorption capacity, mechanical strength, and size and chemical selectivity. In order to tailor these properties for targeted applications in ionic environments, it is imperative that we thoroughly understand the character of these polymer-ion interactions and their arrangement within the bulk hydrogel. In order to do so, however, non-traditional methods of analysis must be employed.</div><div>This dissertation focuses on a model part-ionic hydrogel system, poly(sodium acrylate-co-acrylamide), in order to assess not only the polymer-counter-ion interactions but also the impact of gel ionic fraction on these interactions and the responses which they induce in gel performance properties. A model alkali (NaCl), alkaline earth (CaCl2), and transition (CuSO4) metal salt are employed to investigate changes in polymer properties from the macroscale to the nanoscale. The aim of this dissertation is to lay the foundation for the development of fundamental structure-property relationships by which we may fully understand the ionically-induced performance properties of polyelectrolyte networks.</div>

The development of organic-inorganic hybrid materials is of great interest in thermoelectrics for its potential to combine the desirable characteristics of both classes of materials. Thermoelectric materials must combine low thermal conductivity with high electrical conductivity, but in most materials, thermal and electrical conductivity are closely related and positively correlated. By combining the low thermal conductivity, flexibility, facile processing, and low cost of organic components with the high electrical conductivity and stability of inorganic components, materials with beneficial thermoelectric properties may be realized. Here, we describe the synthesis and characterization of anthracene-containing organic-inorganic hybrid materials for thermoelectric purposes. Specifically, POSS-ANT was synthesized when aminopropylisobutyl-POSS was functionalized with a single anthracene unit via DCC-mediated amide formation. Acrylate-POSS was functionalized with multiple anthracene units in a Heck coupling reaction to synthesize System 1. System 2 was developed through a two-step synthetic process. In the first reaction, (3- acryloxypropyl)methyl dimethyoxy silane was functionalized with anthracene at the 9- position through a Heck coupling reaction. The second reaction was a base-catalyzed solgel process to form polymeric nanoparticles. Finally, System 3 was synthesized through a similar process to System 2, though polymers formed in the initial step. The System 3 precursor was to be developed through a potassium carbonate-catalyzed ether synthesis from 3-(bromopropyl)trimethoxysilane and 9-anthracene methanol, followed by a basecatalyzed sol-gel process to form nanoparticles. The precursor was never isolated because of premature polymerization during the precursor synthesis step, and polymeric nanoparticles were obtained for System 3 during the sol-gel process. These materials were characterized by TEM to reveal the nanostructures that formed upon evaporation from solution. Future work will focus on the characterization of thermoelectric parameters and incorporation into thermoelectric devices.

Electrochemical diazonium grafting offers versatile functionalization of chemically inert graphite under mild condition, which is particularly suitable for CNT composite modification. Tetrafluorinated carboxylphenyl diazonium grafting provides the most controllable functionalization chemistry allowing near monolayer levels of functionality on carbon nanotubes. The functional density was successfully quantified by anion selective dye-assay and X-ray photoelectron spectroscopy (XPS) of thiol-Au self-assembled monolayers (SAM) as a calibration reference. This technique enables monolayer functionality at the tips of carbon nanotube membranes for biomimetic pumps and valves as well as thin conductive layers for CNT-based high area electrochemical support electrodes. Double-walled carbon nanotube (DWCNT) membranes were functionalized with sterically bulky dye molecules with amine termination in a single step functionalization process. Non-faradic (EIS) spectra indicated that the functionalized gatekeeper by single-step modification can be actuated to mimic protein channel under bias. This functional chemistry on membranes resulted in rectification factors of up to 14.4 with potassium ferricyanide in trans-membrane electrochemical measurements. One step functionalization by electrooxidation of amines provides simple and promising functionalization chemistry for the application of CNT membranes. Carbon nanotubes (CNTs) are considered a promising catalyst support due to high surface area, conductivity and stability. But very few cases of asymmetric catalysis have been reported using CNTs as support. Three noncovalent functionalization approaches have been carried out to immobilize Rh-Josiphos complex on CNTs for asymmetric hydrogenation of dimethyl itaconate. Coordinated Rh catalyst on CNTs exhibited excellent activity and reuse ability even after seventh run in hydrogenation but no enantiomeric excess as expected for lacking a chiral directing ligand. The catalyst using pyrene absorption gave 100% yield and excellent enantiomer excess (>90%) but suffered from leaching into solution. The phosphotungstic acid (PTA) anchored catalyst gave 100% yield and higher ee (99%) and better reusability over pyrene absorbed catalyst but had significant leaching after the second run. At this point it remains a significant challenge to utilize CNTs as a chiral catalyst support.

FLUORINATED ARENE, IMIDE AND LACTAM-FUNCTIONALIZED DONOR ACCEPTOR CONJUGATED POLYMERS: SYNTHESIS, STRUCTURE-PROPERTY AND DEVICE STUDIES After the discovery of doped polyacetylene, organic semiconductor materials are widely studied as high impending active components in consumer electronics. They have received substantial consideration due to their potential for structural tailoring, low cost, large area and mechanically flexible alternatives to common inorganic semiconductors. To acquire maximum use of these materials, it is essential to get a strong idea about their chemical and physical nature. Material chemist has an enormous role to play in this novel area, including development of efficient synthetic methodologies and control the molecular self-assembly and (opto)-electronic properties. The body of this thesis mainly focuses on the substituent effects: how different substituent’s affect the (opto)-electronic properties of the donor-acceptor (D-A) conjugated polymers. The main priority goes to understand, how different alkyl substituent effect to the polymer solubility, crystallinity, thermal properties (eg: glass transition temperature) and morphological order. Three classes of D-A systems were extensively studied in this work. The second chapter mainly focuses on the synthesis and structure-property study of fluorinated arene (TFB) base polymers. Here we used commercially available 1,4-dibromo-2,3,5,6-tetrafluorobenzene (TFB) as the acceptor material and prepare several polymers using 3,3’-dialkyl(3,3’-R2T2) or 3,3’-dialkoxy bithiophene (3,3’-RO2T2) units as electron donors. A detail study was done using 3,3’-bithiophene donor units incorporating branched alkoxy-functionalities by systematic variation of branching position and chain length. The study allowed disentangling the branching effects on (i) aggregation tendency, intermolecular arrangement, (iii) solid state optical energy gaps, and (iv) electronic properties in an overall consistent picture, which might guide future polymer synthesis towards optimized materials for opto-electronic applications. The third chapter mainly focused on the structure-property study of imide functionalized D-A polymers. Here we used thiophene-imide (TPD) as the acceptor moiety and prepare several D-A polymers by varying the donor units. When selecting the donor units, more priority goes to the fused ring systems. One main reason to use imide functionality is due to the, open position of the imide nitrogen, which provides an attaching position to alkyl substituent. Through this we can easily manipulate solubility and solid state packing arrangement. Also these imide acceptors have low-lying LUMOs due to their electron deficient nature and this will allow tuning the optical energy gap by careful choice of donor materials with different electron donating ability. The fourth chapter mainly contribute to the synthesis and structure property study of a completely novel electron acceptor moiety consist of a unsaturated pyrrolidinone unit known as Pechmann dye (PD) core. Pechmann dyes are closely related to the Indigo family. This can refer as 3-butenolide dimer connected via an alkene bridge, containing a benzene ring at the 5 and 5’ positions of the lactone rings. We have prepared several D-A polymers using this PD system with benzodithiophene (BDT) as the donor unit. Different to common D-A polymers the HOMO and LUMO of the PD acceptor moiety are energetically located within the gap of the BDT, so that the electronic and optical properties (HOMO-LUMO transition) are dictated by the PD properties. The promising electronic properties, band gaps, high absorption coefficients and broad absorption suggest this new D-A polymers as an interesting donor material for organic solar cell (OSC) applications.

Donor-acceptor copolymers have received a great deal of attention for application as organic semiconductors, in particular as the active layers in low-cost consumer electronics. The functional groups grafted to the polymer backbones generally dictate the molecular orbital energies of the final materials as well as aid in self-assembly. Additionally, the side chains attached to these functional groups not only dictate the solubility of the final materials, but also their morphological characteristics. The bulk of the research presented in this dissertation focuses on the synthesis and structure-property relationships of polymers containing novel acceptor motifs. Chapter 2 focuses on the synthesis of 1,2-disubstituted cyanoarene monomers as the acceptor motif for copolymerization with known donors. It was found that cyanation of both benzene and thiophene aromatic cores resulted in a decrease of the molecular orbital energy levels. Additionally, the small size of this functional group allowed favorable self-assembly and close π-stacking to occur relative to related acceptor cores carrying alkyl side chains as evidenced by UV-Vis and WAXD data. Chapter 3 describes the systematic variation of side chain branching length and position within a series of phthalimide-based polymers. Branching of the side chains on bithiophene donor units resulted in the expected increase in solubility for these materials. Furthermore, a correlation was found between the branching position, size, and the HOMO energy levels for the polymers. Additionally, it was demonstrated that branching the alkyl side chains in close proximity to polymer backbones does not disrupt conjugation in these systems. A novel acceptor motif based on the 1,3-indanedione unit is presented in Chapter 4. Despite the stronger electron withdrawing capability of this functional group relativeto phthalimide, it was found that polymers based on this unit have the same HOMO molecular orbital energy levels as those presented in Chapter 3. It was found, however, the presence of orthogonal side chains greatly enhanced the solubility of the final polymers. Additionally, UV-Vis and WAXD measurements revealed that thermal annealing had a profound effect on the ordering of these polymers. Despite the presence of orthogonal side chains, long range order and close π-stacking distances were still achieved with these materials. Finally, alkynyl “spacers” were used in Chapter 5 to separate the solubilizing alkyl side chains from the polymer backbones on bithiophene donor monomers. The alkynyl groups allowed for conjugated polymer backbones to be achieved as well as low HOMO energy levels. A correlation between the side chain size, π-stacking distances and HOMO-LUMO energy levels was measured in this polymer series.

Thermoelectric materials are playing a larger role in the global effort to develop diverse, efficient, and sustainable energy technologies: primarily through power-generating thermoelectric modules. The principal components of thermoelectric modules are solid-state thermoelectric materials – typically heavily doped semiconductors – that convert heat directly into electricity. However, this conversion efficiency is too low to supplant traditional energy technologies – severely limiting the distribution of clean and sustainable thermoelectric energy technologies. Efforts to enhance thermoelectric efficiency, which have been underway for decades, have been slow to realize appreciable gains in thermoelectric efficiency. However, a key advance in improving efficiency – the New Paradigm in thermoelectric material research – has been the development of thermoelectric nanocomposites. Thermoelectric nanocomposites show improved efficiency; however, they are often synthesized from highly toxic elements via energetically intense and costly synthesis procedures. Therefore, this research focuses on the discovery and development of a novel procedure for synthesizing thermoelectric nanocomposites – attrition enhanced nanocomposite synthesis – from open cage-like skutterudite-based materials. With further optimization, high-performance power-generating thermoelectric materials can be produced via this technique. Therefore, attrition-enhanced nanocomposite synthesis may play a small, though instrumental, role in achieving sustainable electrical power. / Graduation date: 2012 / Access restricted to the OSU Community at author's request from Jan. 6, 2012 - Jan. 6, 2013

Materials science today is a multidisciplinary effort comprising an accelerated convergence of diverse fields spanning the physical, applied, and engineering sciences. This diversity promises to deliver the next generation of advanced functional materials for a wide range of specific applications. In particular, the past decade has seen a growing interest in the development of nanoscale materials for sophisticated technologies. Aqueous colloidal microgels have emerged as a promising class of soft materials for multiple biotechnology applications. The amalgamation of physical, chemical and mechanical properties of microgels with optical properties of nanostructures in hybrid composite particles further enhances the capabilities of these materials. This work covers the general areas of responsive polymer microgels and their composites, and encompasses methods of fabricating microgel-based drug delivery systems for controlled and targeted therapeutic applications. The first part of this thesis is devoted to acquainting the reader with the fundamental aspects of the synthesis, functionalization and characteristic properties of stimulus-responsive microgels constructed from poly(N-isopropylacrylamide) (poly(NIPAm)) and other functional comonomers. In particular, the role of electrostatics on the swelling-deswelling transitions of polyampholyte microgels upon exposure to a range of environmental stimuli including pH, temperature, and salt concentration are discussed. The templated synthesis of bimetallic gold and silver nanoparticles in zwitterionic microgels is also described. The latter part of this thesis focuses on the rational development of microgel-based drug delivery systems for controlled and targeted drug release. Specifically, the development of a biofunctionalized, pH-responsive drug delivery system (DDS) is illustrated, and shown to effectively suppress cancer cells when loaded with an anticancer agent. In another chapter, the design of tailored hybrid particles that combine the thermal response of microgels with the light-sensitive properties of gold nanorods to create a DDS for photothermally-induced drug release is discussed. The photothermally-triggered volume transitions of hybrid microgels under physiological conditions are reported, and their suitability for the said application evaluated. In another component of this work, it is explicitly shown that electrostatic interactions were not needed to deposit gold nanorods on poly(NIPAm)-derived particles, thereby eliminating the need for incorporation of charged functional groups in the microgels that are otherwise responsible for large, undesirable shifts and broadening of the phase transition.

Zeolites are crystalline aluminosilicates with diverse structures and uniform porosities. They are widely used as catalysts, adsorbents and ion-exchangers in industry. Direct or post modifications optimize the performance of zeolites for different applications. In this thesis, IZM-2 and TON-type zeolites were synthesized, modified and studied. In addition, FAU-type zeolite and silicoaluminophosphate (SAPO) molecular sieves were applied as templates for the preparation of microporous carbons. In the first part of this thesis, the IZM-2 zeolite with an unknown structure was synthesized. We focused on the increasing the secondary porosity and the varied framework compositions upon post modifications. The structure determination of this IZM-2 zeolite was hindered by the small size of crystals. In the second part of this thesis, the synthesis composition was directly modified in order to increase the crystal sizes. IZM-2 crystals were enlarged by excluding the aluminium atoms from the framework. The micropores of the obtained pure-silica polymorphs were activated by ion-exchanging alkali-metal ions with protons. Typically, TON-type zeolites that are synthesized at hydrothermal conditions under stirring have needle-shaped crystals. In the third part of this thesis, snowflake-shaped aggregates were produced by using static hydrothermal conditions for the synthesis of TON-type zeolites. The effects of synthesis parameters on the growth and morphology of crystals were discussed in detail. In the last part of this thesis, microporous carbons with a structural regularity were prepared by chemical vapour deposition (CVD) of propylene using a silicoaluminophosphate (SAPO-37) template. Compared to the conventional zeolite templates, the SAPO template could be removed under mild conditions, without using hydrofluoric acid, and the generated carbons had a large specific surface area and a high fraction of ultrasmall micropores. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.</p>

This thesis aims to provide insight into the fundamental electrochemical processes taking place when cycling SnO2 in lithium-ion batteries (LIBs). Special attention was paid to the partial reversibility of the tin oxide conversion reaction and how to enhance its reversibility. Another main effort was to pinpoint which limitations play a role in tin based electrodes besides the well-known volume change effect in order to develop new strategies for their improvement. In this aspect, Li+ mass transport within the electrode particles and the large first cycle charge transfer resistance were studied. Li+ diffusion was proven to be an important issue regarding the electrochemical cycling of SnO2. It was also shown that it is the Li+ transport inside the SnO2 particles which represents the largest limitation. In addition, the overlap between the potential regions of the tin oxide conversion and the alloying reaction was investigated with photoelectron spectroscopy (PES) to better understand if and how the reactions influence each other`s reversibility. The fundamental insights described above were subsequently used to develop strategies for the improvement of the performance and the cycle life for SnO2 electrodes in LIBs. For instance, elevated temperature cycling at 60 oC was employed to alleviate the Li+ diffusion limitation effects and, thus, significantly improved capacities could be obtained. Furthermore, an ionic liquid electrolyte was tested as an alternative electrolyte to cycle at higher temperatures than 60 oC which is the thermal stability limit for the conventional LP40 electrolyte. In addition, cycled SnO2 nanoparticles were characterized with transmission electron microscopy (TEM) to determine the effects of long term high temperature cycling. Also, the effect of vinylene carbonate (VC) as an electrolyte additive on the cycling behavior of SnO2 nanoparticles was studied in an effort to improve the capacity retention. In this context, a recently introduced intermittent current interruption (ICI) technique was employed to measure and compare the development of internal cell resistances with and without VC additive.