Thesis (Ph.D.)--University of Delaware, 2006. / Principal faculty advisor: Darrin J. Pochan, Dept. of Materials Science & Engineering. Includes bibliographical references.

Thesis (Ph.D.)--University of Delaware, 2007. / Principal faculty advisor: Joel P. Schneider, Dept. of Chemistry & Biochemistry. Includes bibliographical references.

Thesis (Ph.D)--Chemistry and Biochemistry, Georgia Institute of Technology, 2009. / Committee Chair: Lyon, Louis; Committee Member: Breedveld, Victor; Committee Member: Bunz, Uwe; Committee Member: Collard, David; Committee Member: Srinivasarao, Mohan. Part of the SMARTech Electronic Thesis and Dissertation Collection.

No description available.

Thesis (Ph.D.)--University of Nebraska-Lincoln, 2008. / Title from title screen (site viewed Feb. 17, 2009). PDF text: xii, 219 p. : ill. (some col.) ; 5 Mb. UMI publication number: AAT 3328256. Includes bibliographical references. Also available in microfilm and microfiche formats.

Nanoscale colloids and nanoparticles (NPs), have recently emerged as a new class of materials that possess photonic, plasmonic, and/or catalytic emergent properties. However, methods for their rational fabrication into materials with designed structural organization remain to be established. Self-assembly -- the idea that NPs can find each other and spontaneously form a targeted macroscale structure with prescribed microscale organization -- is attractive in this context, particularly because it potentially lends itself to facile, large-scale manufacturing. Such a process, however, relies on a combination of interactions and shape effects for the formation of ordered long-range morphologies and a detailed molecular understanding of the governing physics for these systems remains an open question. In an attempt to reduce the complexity of such systems, a major thrust has been to use two NP sub-populations grafted with complementary single stranded DNA (DNA-NPs). The base pairing of these strands drives their spontaneous organization into crystalline arrays. DNA-mediated self-assembly provides a powerful tool to experimentally realize three dimensional crystalline ordering of NP networks; however, the majority of works within this field have focused on an isotropic, purely attractive interaction motif. While successful in controlling NP ordering, the usage of such symmetric designs severely restricts the range of accessible morphologies. This thesis systematically addresses the various limitations imposed by such a design strategy through both theoretical modeling of DNA-NPs interactions and inverse design of optimized self-assembly building blocks. We first relax the assumption that enthalpy completely dominates self-assembly by directly accounting for the effects of chain-chain repulsion as well as entropic frustrations that results from varying the mixing stoichiometry. We then build in the effect of utilizing anisotropy as a structural motif through the development of a scaling theory that captures the interplay between the chain dynamics and local curvature that results in the formation of non-trivial anisotropic coronas. The effects of anisotropy on both the local morphology and long-range crystalline ordering can then be model through the usage of mean-field and perturbation theories. The resulting composite model enables us to directly study how nano-scale phenomena drive micron-scale self-assembly. Lastly, theoretical developments are combined with a genetic algorithm optimization process into an inverse design framework that allows for an a priori design of molecular building blocks such that they spontaneously pack into any desired lattice morphologies. This strategy serves to address the long-standing challenge of nanomaterials design where one can take arbitrary nano-scale objects and arrange them into desired three-dimensional lattices that posses interesting, emergent properties.

In Chapter 1-3, properties and applications of block copolymers, synthetic methods especially living anionic polymerization as well as the development of the SAAP concept with some of previous successful examples are reviewed. Experimental methods, including the design and establishment of a special high-vacuum system, size exclusion chromatography and laser light scattering, are explained. / In Chapter 4, living anionic polymerization of alpha,o-di bromobutyl end-capped PI-b-PS-b-PI triblock copolymers and the end-capping reaction with 1,4-dibromobutane at the end of polymerization are described, including a in-depth analysis of the reaction mechanism that involves the dimerization of two living oligomer chain during the reaction of living polymeric anions with haloalkanes, i.e., the Wurtz-type coupling reaction. The self assembly and coupling reaction of 1,4-dilithio-1,1,4,4-tetraphenylbutane (DD2-) in n-hexane to form long (PI- b-PS-b-PI)10 multiblock chains are discussed. The coupling efficiencies with and without the self assembly are compared to demonstrate the principle of SAAP. However, the coupling reaction with dianion linker is troublesome because a trace amount of impurities in the solvent can remove its activity. / In Chapter 5, a method of improving the coupling efficiency is described. In this method, PI-b-PS-b-PI triblock copolymers is end-capped with avo-dicarboxylic acid groups via a reaction between living anions and carbon dioxide. Such prepared HOOC-ISI-COOH chains can be coupled with 1,6-hexamethylenediamine (HDA) in the presence of 1,3-dicyclohexylcarbodiimide (DCC) after the self assembly. The size exclusion chromatography (SEC) analysis shows that the SAAP method mainly leads to the formation of triblock copolymer chain dimers and the coupling efficiency is close to 50%. There is no coupling in THF without the self assembly. Further, a much better method of using alpha,o-diacyl chloride end-capped PI-b-PS-b-PI triblock copolymer chains in SAAP to prepare long multiblock copolymer chains is described. Using this recently developed method, we are able to prepared long ∼90-block copolymer chains (PI-b-PS-b-PI)30 which clearly shows the advantage of using SAAP to prepare long multiblock copolymers with a controllable sequence and different block lengths. / In this thesis, we have proposed and developed a novel method: The Self-Assembly Assisted Polypolymerization (SAAP). Namely, using the self-assembly of A-B-A triblock copolymers with two active end groups in a selective solvent for the A-block to concentrate and expose the active end groups on the periphery of the resultant core-shell polymeric micelles, we can effectively couple each two active ends on different chains together to form a long multiblock copolymer chain with its sequence and block length well controlled by the initial triblock copolymer. To accomplish this project, we first built a high-vacuum system for living anionic polymerization and then synthesized and characterized narrowly distributed polyisoprene-b-polystyrene- b-polyisoprene (PI-b-PS-b-PI) triblock copolymer chains with their both ends capped respectively with bromobutyl and carboxylic acid active groups. The self assembly of such prepared triblock copolymers in n-hexane, a selective solvent for PI, was studied by a combination of static and dynamic laser light scattering (LLS). Finally, the self-assembled end-functionalized PI-b-PS-b-PI chains were coupled together by difunctional small molecules (linkers) to form long multiblock copolymers with a controlled structure. / Hong, Liangzhi. / "Aug 2007." / Adviser: Chi Wu. / Source: Dissertation Abstracts International, Volume: 69-02, Section: B, page: 1036. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract in English and Chinese. / School code: 1307.

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The question about the origins of life often appears as a difficult question to answer. A more reliable candidate molecule for the chemical origins of life would be a molecule that is capable of making copies of itself from simple precursors. With the finding of the catalytic activities of RNA molecules by Thomas Cech and Sid Altman in late 1980s, the term ribozyme was introduced to define an RNA molecule with catalytic activity. The RNA World is a conceptual period in the early stages in the development of life because RNA simultaneously possesses evolvability and catalytic function. An RNA molecule that could evolve in such a fashion is likely to have been one of the Earth's first life forms. The most important problem facing the RNA World is the difficulty of prebiotic synthesis of RNA. Different prebiotic environments could provide the right reaction conditions for synthesis of catalytically active RNA molecules. Most importantly, these environments can support new ways to assemble monomers into polymers. In order to understand and demonstrate how small inactive RNA oligomers can self-assemble into an autocatalytic ribozyme molecule, here I have used the Azoarcus Group I intron. First, the fragmentation and the self-assembly reactions were done using the natural IGS-tag combination of the Azoarcus group I intron, which is GUG/CAU. The main purpose was to experimentally demonstrate that the ribozyme can be broken down into five or more shorter RNA fragments and these fragments can self-assemble into a catalytically active covalent full-length molecule. Then, with the successful demonstration that five inactive RNA fragments can self-assemble, the next step to test the other possible breaking locations with mutated IGS/tag combinations. A new IGS/tag pair GCG-CGU also successfully demonstrated the five-piece self-assembly reaction. Finally, we tested these reactions in different Mg2+ concentrations to optimize the self-assembly reactions. By focusing not only one single reaction but on a collection of different sequence requirement combinations and with the development of evaporation and subsequent rehydration by spinning down methods this study successfully illustrates that covalent self-assembly from inactive RNA oligomers is possible. Therefore, this thesis work focuses on a more broader aspect of intermolecular interactions in the study of the RNA World, as illustrated in following chapters.

Thesis (Ph.D.)--University of Delaware, 2006. / Principal faculty advisors: Dionisios G. Vlachos and Raul F. Lobo, Dept. of Chemical Engineering Includes bibliographical references.