Excepting agricultural based products, which themselves require a great deal of energy to produce, our supply of natural resources such as minerals, metal ore, fresh water, coal, oil and natural gas are all limited in supply. The depletion of these substances is imminent and this knowledge weighs heavily on humankind. The utilization of CO2 for the production of polycarbonates is one attempt at exploiting a profoundly abundant and renewable resource. The importance of research in this and similar fields justifies the detailed study of the chemicals and procedures involved with this chemistry. This current work concentrates on the fundamental study of transition metal Schiff base complexes that have shown a great deal of promise in their ability to catalyze the copolymerization of CO2 and epoxide to form aliphatic polycarbonates. A new chromium(III) Schiff base complex has been synthesized and evaluated for its ability to catalyze the formation of polymer. The ligand employed bears an N2O2 coordination sphere identical to the widely utilized chromium(III) and cobalt(III) salen catalysts. This complex was shown to be active towards the copolymerization of CO2 and cyclohexene oxide. Although the activity was less than that seen with chromium(III) salen complex, the study demonstrates that new ligand systems are available beyond salen and deserve further attention. A class of manganese(III) Schiff base complexes was also synthesized and evaluated as catalysts. Although crystallographic data has shown that these complexes are structural analogs to chromium(III) salens, the difference in metal center leads to a nearly complete elimination of catalytic activity. Such a marked difference has been taken advantage of by using this very low activity to study the ring-opening of epoxide in the initial step of the copolymerization both mechanistically and kinetically. It has also been utilized in an evaluation of the coordination chemistry of the polymerization process. This has led to some valuable conclusions about the nature and role of the metal center that previously have not been studied. Manganese(III) salen complexes were also synthesized and evaluated in an effort to compare these important ligands to other Schiff bases and confirm the findings mentioned above.

A prominent goal of scientists is to develop products and processes to meet the ever-growing needs of society. Today's needs include products that are economical, specialized, and made through processes with minimal impact on the environment. One such product that serves an important and widespread need is poly(bisphenol A carbonate) for its physical properties and ease of synthesis and processing. However, this polymer does not meet the growing need of being environmentally benign as production involves carcinogenic, chlorinated solvents and toxic monomers that can leach out from the polymer product. An answer to this new demand is the development of a different process for the production of polycarbonate plastics utilizing carbon dioxide and epoxides. Carbon dioxide is an attractive monomer that is cheap and nontoxic, and its utilization signifies an important contribution to counteract global greenhouse emissions. The stability of carbon dioxide has posed a significant and complex challenge towards its utilization. Epoxides are attractive since they are synthesized from a wide variety of olefins, both naturally occurring and those derived from petroleum. The exploration of catalysts to facilitate the coupling of epoxides to carbon dioxide to afford polycarbonates has been under investigation in the Darensbourg lab for fifteen years, and has lead to the development of several successful systems such as zinc bisphenoxides and chromium salens. This dissertation focuses on the development of another successful catalyst system, chromium tetramethyltetraazaannulene, and further elucidation of the mechanism by which polycarbonates are formed. Herein, aspects of the copolymerization process using this system will be discussed in detail, such as cocatalyst and pressure dependence, catalyst derivatization, and kinetic and mechanistic investigations. The end result of these investigations is the development of the most active chromium-based catalyst for the copolymerization of cyclohexene oxide and carbon dioxide and a better understanding of how the copolymer product is produced.

This thesis aims to investigate the effects of gamma radiation on the properties of polycarbonate, an engineering thermoplastic which has a wide range of applications. A commercial grade polycarbonate resin, after being shaped into the required specimen forms by injection molding, was irradiated with different doses up to 180 kGy. Tensile strength was found to decrease with increasing dose. The lowest values of tensile modulus, flexural modulus and flexural strength were obtained at 96 kGy, which is also the dose at which molecular weight values showed a minimum. No remarkable changes in Shore D hardness values and NMR spectra were observed. The ATR-FTIR spectra showed that irradiation was effective on carbonyl groups in the structure. The glass transition temperatures of the specimens irradiated up to the maximum dose were lower than those of the non-irradiated specimens. The onset of weight loss at lower temperatures and steeper weight loss behavior in the TGA curves indicated decreasing thermal stability of the polymer with increasing dose.

Pressing demands for high power and high energy densities in novel electrical energy storage units have caused reconsiderations regarding both the choice of battery chemistry and design. Practical concerns originating in the conventional use of flammable liquid electrolytes have renewed the interests of using solvent-free polymer electrolytes (SPEs) as solid ionic conductors for safer batteries. In this thesis work, SPEs developed from two polymer host structures, polyethers and polycarbonates, have been investigated for all-solid-state Li- and Li-ion battery applications. In the first part, functional polyether-based polymer electrolytes, such as poly(propylene glycol) triamine based oligomer and poly(propylene oxide)-based acrylates, were investigated for 3D-microbattery applications. The amine end-groups were favorable for forming conformal electrolyte coatings onto 3D electrodes via self-assembly. In-situ polymerization methods such as UV-initiated and electro-initiated polymerization techniques also showed potential to deposit uniform and conformal polymer coatings with thicknesses down to nano-dimensions. Moreover, poly(trimethylene carbonate) (PTMC), an alternative to the commonly investigated polyether host materials, was synthesized for SPE applications and showed promising functionality as battery electrolyte. High-molecular-weight PTMC was first applied in LiFePO4-based batteries. By incorporating an oligomeric PTMC as an interfacial mediator, enhanced surface contacts at the electrode/SPE interfaces and obvious improvements in initial capacities were realized. In addition, room-temperature functionality of PTMC-based SPEs was explored through copolymerization of ε-caprolactone (CL) with TMC. Stable cycling performance at ambient temperatures was confirmed in P(TMC/CL)-based LiFePO4 half cells (e.g., around 80 and 150 mAh g-1 at 22 °C and 40 °C under C/20 rate, respectively). Through functionalization, hydroxyl-capped PTMC demonstrated good surface adhesion to metal oxides and was applied on non-planar electrodes. Ionic transport behavior in polycarbonate-SPEs was examined by both experimental and computational approaches. A coupling of Li ion transport with the polymer chain motions was demonstrated. The final part of this work has been focused on exploring the key characteristics of the electrode/SPE interfacial chemistry using PEO and PTMC host materials, respectively. X-ray photoelectron spectroscopy (XPS) was used to get insights on the compositions of the interphase layers in both graphite and LiFePO4 half cells.

There has been a growing demand for specific linear alpha olefins in the polyethylene industry in order to control polymer rheology. This growing demand thereby increases the need for highly active and selective ethylene oligomerization catalysts. Chromium-based catalysts continue to be of high interest for this application due to this metal’s versatility in both selective and non selective ethylene oligomerization. Ligand design is an important consideration in oligomerization chemistry: the ability of the ligand to stabilize low valent chromium and to support a two-electron redox process will allow the catalytic systems to follow the selective ring expansion mechanism for oligomerization. Chelating aminophosphane based ligands, previously studied by our group, have been shown to support both tri- and tetramerization of ethylene. We have explored modifications of one of the NP arms by replacing with a different coordinating group in an attempt to further stabilize the monovalent state of chromium and increase selectivity. Other ligands explored in this work are pyrrole based ligands, which have shown high activity and selectivity towards ethylene oligomerization. One example of this is the commercial Chevron-Phillips system. Recently, the co-polymerization of CO2 with epoxides has been studied as an environmentally friendly route to convert CO2 into biodegradable polymers. The first successful catalytic system to achieve these results consisted of a diethyl-zinc complex. More recently, aluminum, chromium, cadmium and cobalt have been studied as polycarbonate catalysts. To date, the only reported chromium catalysts for CO2-epoxide copolymerization are Cr-salen and Cr-porphyrin complexes, studied by Darrensbourg and Holmes, respectively. We were particularly interested in finding new chromium-based complexes able to catalyze epoxide/CO2 copolymerization by using molecules with the nitrogen donor motif embedded in different functions such as neutral pyridines with anionic pendants, pyrroles with either imine or amine pendants, or a combination of these.

Zugl.: Siegen, Univ., Diss., 2008

Techn. Hochsch., Diss., 2003--Aachen.

Nürnberg, Universiẗat, Diss., 2002--Erlangen.

Techn. Hochsch., Diss., 2004--Aachen.

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / O policarbonato de bisfenol A (PCBFA) à um poliÃster, com repetiÃÃo de estrutura quÃmica das molÃculas de bisfenol A (BFA), que acumula um conjunto bem balanceado de propriedades, tais como: transparÃncia, estabilidade tÃrmica e dimensional, resistÃncia mecÃnica, antichama; permitindo classificÃ-lo como plÃstico de engenharia. Ele à um material utilizado em garrafÃes retornÃveis para acondicionamento de Ãgua mineral. O processo de fabricaÃÃo dos garrafÃes à de grande importÃncia, pois objetiva a produÃÃo de um material uniforme, que de certa maneira garante qualidade para resistir Ãs intempÃries do tempo e aos diversos processos de envasamento de Ãgua, estocagem e distribuiÃÃo. Os ÃrgÃos governamentais regulamentaram que o tempo de vida Ãtil das embalagens à somente de trÃs anos. A validade da Ãgua em garrafÃes lacrados varia de 60 a 120 dias. Depois de aberto, a recomendaÃÃo à consumir em atà duas semanas. A degradaÃÃo do PCBFA foi estudada utilizando garrafÃes de 20 litros de diferentes anos de fabricaÃÃo (0-15 anos), observou-se o efeito do tempo na mudanÃa das caracterÃsticas e propriedades do material. Verificou-se que a espessura dos garrafÃes diminui com o tempo de fabricaÃÃo. A partir de 8 anos de fabricaÃÃo, possÃveis mudanÃas estruturais, como a descarboxilaÃÃo, diminuiÃÃo da temperatura de transiÃÃo vÃtrea e alteraÃÃo nas propriedades mecÃnicas foram constatadas atravÃs das tÃcnicas de infravermelho (FTIR), Calorimetria ExploratÃria Diferencial (DSC) e por ensaios mecÃnicos de traÃÃo, respectivamente. Por microscopia eletrÃnica de varredura (MEV), verificou-se que a superfÃcie externa apresentou-se com mais alteraÃÃes morfolÃgicas em relaÃÃo à superfÃcie interna. Por anÃlise termogravimÃtrica (TGA), notou-se que o PCBFA da superfÃcie interna tem uma menor estabilidade tÃrmica que a superfÃcie externa do garrafÃo. Por anÃlise de fluorescÃncia foi detectada a presenÃa de BFA em Ãgua destilada mantida em contato com o garrafÃo estocada durante 2 meses. O BFA à o reagente utilizado na sÃntese industrial do PCBFA onde o mesmo à um desregulador endÃcrino que causa alteraÃÃes hormonais no sistema endÃcrino. Pode-se concluir que os garrafÃes de PCBFA sofrem degradaÃÃo com o passar dos anos a ponto do material perder suas principais propriedades, tanto na superfÃcie externa e interna. A relevÃncia maior do estudo evidencia sobre a validade dos garrafÃes e a possÃvel liberaÃÃo de BFA na Ãgua. / The polycarbonate of bisphenol A (PCBFA) is a polye ster with repeating chemical structure of molecules of bisphenol A (BFA), which accumulates a well-balanced set of properties, such as transparency, thermal and dimen sional stability, mechanical strength, flame retardant; allowing classify it as engineerin g plastic. It is a material used in returnable carboys for packaging of mineral water. The manufacturing process of the carboys is of great importance, because it aims the production of a uniform material, which somehow ensures quality to withstand the incl ement weather of weather and the various processes of potting water, stocking and di stribution of carboys. Government agencies have regulated that the time of validity o f the carboys is only three years. The validity of water in sealed bottles ranges from 60 to 120 days. Once opened, the recommendation is to consume within two weeks. The degradation was studied using PCBFA of 20 liters carboys of different fabrication years (0-15 years), we observed the effect of time in changing of the characteristics a nd properties of material. It was found that the thickness of carboys lowers with time of f abrication. From 8 years of manufacturing, possible structural changes, such as decarboxylation, reduction in glass transition temperature and changes in mechanical pr operties were observed via infrared techniques (FTIR), differential scanning calorimetr y (DSC) and tensile test, respectively. By scanning electron microscopy, it w as found that the external surface appeared with more morphological changes in relatio n to the inner surface. By thermogravimetric analysis (TGA), it was noted that the PCBFA the inner surface has a lower thermal stability than the outer surface of t he carboy. By fluorescence analysis, we detected the presence of BFA in distilled water kept in contact with the stored carboy for 2 months. BFA is the reagent used in the industrial synthesis of PCBFA where it is an endocrine disrupter which causes hor monal changes in the endocrine system. It can be concluded that the polycarbonate carboys undergo degradation with passing of the years to the point of the material l osing its main properties, both the outer and inner surface. The most relevant study demonstr ates the validity of carboys and the possible release of BFA in the water