Browsing by Subject "polypeptide"
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Item Metal catalyzed copolymerization processes involving carbon oxides as substrates(Texas A&M University, 2005-11-01) Phelps, Andrea LeeStudies concerning two different copolymerization processes are detailed in this dissertation: propylene oxide/CO2 coupling to afford poly(propylene carbonate) and Nbutylaziridine/ CO coupling to afford poly-??-butylalanoid. The copolymerization of propylene oxide and CO2 to form the industrially useful poly(propylene carbonate) has been investigated employing chromium(salen)N3 complexes as catalysts. Unfortunately the reaction could not be studied in real time via in situ infrared spectroscopy, thereby obtaining detailed kinetic data, because of the copolymer-limited solubility in most solvents. Studies employing batch reactor runs concentrating on varying the cocatalyst, the equivalents of cocatalysts, and the steric and electronic structure of the catalyst through modification of the salen ligand were undertaken. It was discovered that the optimal catalyst for copolymer selectivity vs. the monomeric propylene carbonate was one that contained a salen ligand with an electron withdrawing phenylene backbone and electron donating tert-butyl groups in the phenolate rings. This catalyst was used to investigate the effect of altering the nature of the cocatalyst and its concentration. The coupling of carbon monoxide and aziridines has been shown to be selective for comonomer-alternating enchainment in the presence of PhCH2C(O)Co(CO)4 to afford poly-??-peptoids. The mechanistic aspects of the reaction of CO and Nbutylaziridine by means of in situ infrared spectroscopy employing CH3C(O)Co(CO)3L (L = PPh3 and P(o-tolyl)3) as precatalysts was investigated. It was found the PPh3 precatalyst exists in solution under catalytic conditions as an equilibrium mixture of CH3C(O)Co(CO)3PPh3 and CH3C(O)Co(CO)4, and affords both poly-??-butylalanoid and the corresponding lactam as a side-product. By way of contrast, the P(o-tolyl)3 precatalyst which possesses the sterically bulky and labile phosphine ligand, affords only the acyl cobalt tetracarbonyl species in solution during catalysis with the selective production of the copolymer. Kinetic studies conducted with CH3C(O)Co(CO)3P(otolyl) 3 showed the coupling reaction to have a first order dependence on catalyst, a first order dependence on N-butylaziridine, and only a slight dependence on the concentration of CO over the pressure range 17-69 bar. The working mechanistic model for the copolymerization reaction involves first aziridine insertion into the cobalt-acyl bond, rate determining ring opening by the cobaltate species, followed by the migratory CO insertion.Item Studies of block copolypeptide synthesis, self-assembly, and structure-directing ability(Texas A&M University, 2007-04-25) Jan, Jeng-ShiungThe use of organic compounds as templates to assemble inorganic materials with structures over multiple length scales has received much attention due to the potential applications that can be developed from these materials. Many organisms synthesize organic/inorganic composites with exceptional control over morphology, physical properties, and nanoscale organization of these materials. Materials such as bone, nacre, and silica diatoms are excellent examples of the complex yet highly controllable hierarchically structured materials nature can form at ambient conditions. The ability to mimic these organisms through the design of supramolecular assemblies and use them to direct the growth of hierarchically structured materials has increased significantly in recent years. In this dissertation, block copolypeptide templated inorganic materials were synthesized and characterized using a wide range of analytical techniques. There are three major conclusions from this dissertation. First, the conformation of a polypeptide chain can be used to manipulate the porosity of oxide materials obtained. Second, individual supramolecular objects (vesicles) formed by block copolypeptides can be used as templates to form nanostructured hard materials. Third, polypeptide chemistry and solution conditions can be used to control both the morphology and porosity of the hard materials they assemble. This dissertation also describes preliminary work toward designing the block copolypeptides derivatives for biomimetic inorganic synthesis and gene delivery. This work includes the synthesis of these block copolypeptides derivatives and of the templated oxide materials. Some interesting silica materials such as porous silicas and silica nanocapsules were synthesized using double hydrophilic block copolypeptides derivatives as templates. Also, the preliminary work of using these block copolypeptides derivatives for gene delivery is included and shows these copolypeptide derivatives are potential delivery vehicles.