The recent development of materials with autonomous repair capabilities has opened an exciting new field of polymer science expected to impact nearly every facet of modern society. Similar to natural systems, these "self-healing" materials sense when their structural integrity has been compromised (e.g., due to wear or damage) and respond with a viable repair mechanism. Despite the extraordinary number of successes and advances in this area, a means to ascertain instantaneous knowledge of a material's structural integrity, and more importantly, when it has been compromised, remains a considerable challenge in current systems and materials. To address this challenge, we report recent efforts toward the development of an electronically conductive material that is structurally dynamic and responds to various types of external stimuli. In particular, we have developed new synthetic methodology to prepare a variety of organometallic polymers containing a novel benzobisimidazolylidene or bis(benzoimidazolylidene) ligand, which is comprised of two linearly opposed N-heterocyclic carbenes (NHCs) annulated to a common linker, and various types of transition metals in the polymer's main-chain. Using this approach, polymers with molecular weights up to 10⁶ Da were prepared and cast into robust thin films. Using four-point probe technique, the inherent conductivities of these materials were found to be on the order of 10⁻³ S/cm. Secondly, the dynamics of these polymers were probed in solution using gel permeation chromatography. At specific cross-linker loadings, thermally-responsive gels were obtained. Collectively, these experiments suggested that the essential features for a thermally-responsive, structurally dynamic, conjugated organometallic polymer were developed. Efforts toward probing their ability to display self-healing characteristics in the solid-state are described. The inherent conductivity of the polymers permitted the healing behavior of thin films to be observed by scanning electron microscopy in the absence of a dopant. Long range goals of implementing and utilizing these materials in electronic circuits and other advanced devices are also described. An additional approach towards a dynamic material utilized functional imidazolium-based ionic liquids. A series of functional ionic liquids were produced by appending N-substituents containing pendant halides, alkynes, azides, furans and maleimides. These functional groups allowed for polymerization and crosslinking. The physical properties of the imidazolium monomers, as well as the resulting polymers, could be tuned by altering the anion. When a trifunctional monomer is used in conjunction with the polymerization of difunctional ionic liquids an insoluble crosslinked material forms. This behavior, combined with NHCs ability to bind transition metals as ligands and catalyze various organic transformations, provides potential for this system to be used as a method for catalyst recovery and ultimately catalyst recycling. / text

No description available.

Thesis (Ph. D.)--University of Hong Kong, 2010. / Includes bibliographical references. Also available in print.

Research into conductive organic and organometallic polymers began in 1977 when Heeger, Macdiarmid, and Shirakawa first doped polyacteylene with Iodine. They found that this doping granted the polymer metallic properties increasing conductivity by 11 orders of magnitude.[1] Unfortunately, polyacteylene is highly air-sensitive making it difficult to work with and limiting its applications. Therefore, current research is focused on synthesizing new organic and organometallic conductive polymers. The drive to discover these new polymers stems from their application flexibility and their low production cost. Reported here is the synthesis of novel organometallic polymer precursors. Lead by Dr. Chad Snyder a library of chloro-phenyl based fulvenes, 5,6 fused ring pyridazines, and thallium Cp salts have successfully been synthesized. Research is currently underway to synthesize rhenium and manganese pyridazines through transmetalation of the thallium salts. The off-metal route of synthesis was followed as opposed to the previously reported on-metal route. Characterization was performed by 1H-NMR, 13CNMR, and IR. Additionally, research has begun on bromo-thiophene complexes. So far, bromothiophene fulvenes, pyridazines, and thallium Cp salts have been synthesized and work is currently underway to produced rhenium and manganese pyridazines as well. Characterization was performed by 1H-NMR and 13C-NMR.

Thesis (Ph. D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2005. / Weck, Marcus, Committee Chair ; Jones, Christopher, Committee Member ; Collard, David, Committee Member ; Liotta, Charles, Committee Member ; Bunz, Uwe, Committee Member. Includes bibliographical references.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 128-138). Also available via the Internet.

xxii, 143 p. ; ill. (some col.) A print copy of this title is available through the UO Libraries. Search the library catalog for the location and call number. / There are compelling economic and environmental reasons for using degradable plastics in selected applications and considerable research is now devoted to devising new photodegradable polymers with improved performance. Controlling the degradation of these materials in a prescribed fashion is still a difficult problem because the parameters that influence degradation rates are not completely understood. In order to predict polymer lifetimes, to manipulate when a polymer starts to degrade, and to control the rate of degradation, it is necessary to identify the experimental parameters that affect polymer degradation rates and to understand how these parameters affect degradation. This dissertation describes the results of experiments designed to gain fundamental insight into the factors that affect the rate of polymer photodegradation. The key experimental strategy employed was the incorporation of organometallic dimers into the backbone of the polymer chains, specifically, [CpRMo(CO) 3 ] 2 (CpR = a substituted cyclopentadienyl (· 5 -C 5 H 4 R)). Incorporating these organometallic units into a polymer chain make the polymer photodegradable because the metal-metal bond can be cleaved with visible light. The photogenerated metal radicals can then be trapped by O 2 or chlorine, resulting in degradation of the polymer. Another benefit from incorporating this chromophore into the polymer backbone is that it provides the experimentalist with a convenient spectroscopic handle to monitor degradation rates. Using these model polymers, several experimental factors that can affect polymer photodegradation rates have been explored. For example, experiments showed that radical trap concentration affects degradation rates below, but not above, the polymer glass transition temperature. In addition, degradation rates as a function of irradiation temperature, tensile stress, and time-dependent morphology changes were explored for various polymers. The results of these studies suggest that the ability of the photogenerated radicals to escape the radical cage is the dominant factor in determining photodegradation efficiencies. This dissertation includes previously published and unpublished co-authored material. / Adviser: David R. Tyler

No description available.

The synthesis and properties of novel Metal Organic Frameworks were investigated and reported in this thesis. Thirteen new materials have been synthesized and their properties have been discussed with nine of the structures being solved. The most interesting and useful MOF among the thirteen materials is STAM-1, a copper-based Metal Organic Framework in which the starting linker (Benzene-1,3,5-tricarboxylic acid) undergoes selective in situ monoesterification during the synthesis. The monoesterified BTC can be recovered easily from the MOF, opening up MOF synthesis as a “protection” tool for unexpected selectivity in preparative chemistry that is difficult to accomplish using standard organic chemistry approaches. The selective linker derivatisation leads to the formation of a porous MOF with two types of accessible channel; one hydrophilic lined by copper and the other hydrophobic, lined by the ester groups. The unique structure of the pores leads to unprecedented adsorption behaviour, which reacts differently to gases or vapours of dissimilar chemistry and allows them to access different parts of the structure. The structural flexibility of STAM-1 shows significant differences in the kinetics of O₂ and N₂ adsorption, showing potential for new materials to be developed for air separation. Having two types of channel systems, adsorption can be switched between the two channels by judicious choice of the conditions; a thermal trigger to open the hydrophilic channel and a chemical trigger to open the hydrophobic channel. The storage and release capability of NO in STAM-1 was investigated for use in biomedical applications. Successful studies showed the strength of the antibacterial effects of NO loaded STAM-1, by using three different bacterial strains as a test of performance and were found to be bactericidal. Furthermore the antibacterial effects of NO free STAM-1 were also probed and found to be bactericidal even with low concentrations of the material such as 5 wt%. STAM-1 showed some complex magnetic behaviour by displaying strong antiferromagnetic properties at room temperature and ferromagnetic properties at lower temperatures. The antiferromagnetic coupling was observed within the dimer and ferromagnetic coupling between the dimers. This property of ferromagnetism can only be attributed to the corporation of magnetic dimers in the framework. STAM-2 displays a different magnetic behaviour than STAM-1 which shows paramagnetic properties at room temperature and antiferromagnetic properties at lower temperatures. Other novel MOFs were also successfully characterised and their properties were investigated for potential applications.

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy