Doctor of Philosophy, The Ohio State University, 2022, Chemistry

Numerous biological processes are carried out by the detection and interaction of small organic molecules, which assemble to form larger macrostructures. In Nature these processes are highly controlled, as small deformities can have deadly implications. Amino acids, peptides, nucleic acids, and proteins arrange with remarkable specificity into distinct structures that adapt, reorganize, and interact with their surroundings to enable the biological functions that characterize life. To truly duplicate the complexity, specificity, and operation of natural systems, however, it is essential to comprehend and design synthetic building blocks with controllable assembly properties and interactions. As an approach for creating responsive and adaptive materials, the self-assembly of organic peptide-based molecules into nanostructures was examined in the following studies. It is hoped that the advancements reported here in pH-controllable self-assembly, pathway control, and hierarchical structures can be further used to create nanomaterials for biomedical and optoelectronic applications.

Committee: Jon Parquette (Advisor) Subjects: Chemistry; Molecules; Morphology; Nanoscience; Nanotechnology; Organic Chemistry

Doctor of Philosophy (Ph.D.), University of Dayton, 2019, Materials Engineering

The motivation for this effort is the desire of the United States Air Force (USAF) to implement slow crack growth damage tolerance lifing (DTL) for its polymer matrix composite (PMC) components. Implementing DTL for PMCs would allow the USAF to life manage its PMC components in a similar manner to its metal components. To realize this goal, the USAF must be able to characterize damage in PMCs with a fidelity that is sufficient to generate a reliable prediction of remaining life or strength with existing damage propagation models. To that end, a statistical meta-analysis of barely visible impact damage (BVID) in composites is conducted using data from the literature to understand the scope of the BVID problem. The analysis performed shows that delamination morphologies that have hidden delaminations (delaminations that are not detectable with normal incidence ultrasonic nondestructive evaluation (NDE), the current sustainment characterization tool) are likely to occur in 1/3 of barely visible impacts. Characterization of hidden delaminations is therefore, a significant challenge to implementing DTL. Statistical meta-analysis of the BVID data from the literature shows that most (92%, 95% CI (0.81, 1.03), n = 25) of the time a cone shaped BVID field results when the PMC has 90° plies at the center of the laminate and the cross-section view of the BVID morphology was taken along the center plies. This delamination morphology information can be used a priori to inform the NDE inspection direction and optimize the sensitivity of the inspection to defects of interest. In order to detect and characterize hidden delaminations with a single sided, fieldable NDE inspection (USAF constraints on BVID characterization) the technique of oblique angle pulse-echo ultrasound is investigated. An understanding of oblique angle ultrasound wave propagation, reflection and diffraction are presented. Model results suggest oblique angle pulse-echo ultrasound is sensitive to hidden del (open full item for complete abstract)

Committee: Amanda Criner PhD (Advisor); Donald Klosterman PhD (Committee Chair); Terry Murray PhD (Committee Member); Shamachary Sathish PhD (Committee Member) Subjects: Aerospace Engineering; Aerospace Materials; Engineering; Materials Science

Doctor of Philosophy, Case Western Reserve University, 2014, Chemistry

Core-substituted naphthalenediimides (core-substituted NDIs) were incorporated into rod-like molecules and oligomers through reaction at the imide nitrogen positions. N,N'-Di(4-bromophenyl)-2,6-di(N-alkylamino)-1,4,5,8-naphthalenetetracarboxydiimide was synthesized in only three steps, and used as a versatile platform to prepare extended structures by reaction with thiophene substrates using Suzuki-coupling conditions. The optoelectronic properties of the new compounds were examined by UV/vis absorption spectroscopy, fluorescence spectroscopy, cyclic voltammetry and theoretical calculations. The imide substituents had little effect on the optical and electrochemical properties of core-substituted NDIs in solution. A bathochromic shift of the absorption was observed upon film formation, accompanied by quenching of fluorescence. These observations are consistent with increased inter-molecular interactions between core-substituted NDI moieties in the solid state. All compounds were tested in organic solar cells by blending with poly(3-hexylthiophene) (P3HT), and several showed a photovoltaic effect, demonstrating their potential as electron acceptors in organic solar cell. The best solar cell was observed for core-substituted NDI with 4-(thiophen-2-yl)phenyl imide substituents (5a), showing a power conversion efficiency of 0.57% and a large open circuit voltage of 0.87 V. This approach allows new structure-property relationship studies of non-fullerene acceptors in organic solar cells, where one can vary the imide substituent to optimize photovoltaic parameters while keeping the optical and electrochemical properties constant. To study the structure-property relationships of core-substituted NDIs as acceptors for organic solar cells, a series of 2,6-dialkylamino NDI compounds with various substituents were synthesized, characterized and tested in bulk heterojunction solar cells by blending with P3HT. The imide substituents consisted of a linker connected to a thioph (open full item for complete abstract)

Committee: Geneviève Sauvé (Advisor); John Protasiewicz (Committee Chair); Thomas Gray (Committee Member); Carlos Crespo (Committee Member) Subjects: Alternative Energy; Chemistry; Energy; Materials Science; Molecular Chemistry; Molecules; Morphology; Organic Chemistry; Physical Chemistry

Doctor of Philosophy, The Ohio State University, 2011, Chemistry

Part I: Dendron based phosphoramidite ligands functioned differently in palladium catalyzed asymmetric allylic alkylation and generated the product ee% as 23%(S) and 61%(S), respectively. In all, the chiral information from the dendrons has been amplified and the induced chirality is promising in the asymmetric reactions. Part II We developed a strategy of fabricating amphiphilic n/p-type heterojunctions based on L-lysine fabricated with Naphthalenediimide (NDI) linked to Tetraphenylporphyrin (TPP) via glysine at the side chain. Depending on the solvents and the concentrations, it either self-assembled into twisted nanofibers or uniform nanorods, or varied sized vesicles. Notably, simplified symmetrical bolaamphiphiles comprised of a central TPP chromophore flanked on both ends by NDI-lysine moieties generated uniform nanotubes upon facile stacking.

Committee: Jonathan Parquette (Advisor); T. V. RajanBabu (Committee Member); Jovica Badjic (Committee Member); Wu Lu (Committee Member) Subjects: Chemistry