This study attempts to calculate the areas of the cross section and diameter of the CH3 group, COOH group, the length of the carbon chain, and the longtiudinal distance between carbon atoms for each of the three acids. It also attempts to develop a method of measuring the effective diameter of molecules of gases. Equations for these terms as given by MacDougall and experiments were performed and the data applied to the equation.

High temperature polyarylene networks produced through the step-growth thermal cyclopolymerization of mono-ortho-diynylarene (MODA) and bis-ortho-diynylarene (BODA) monomers have been shown to produce high yielding glassy carbon once pyrolyzed at 1000 °C. In this study the homo- and co-polymerization of both monomers will be studied, and the effects of copolymer composition on the processability when applied to carbonization and carbon-carbon composites. The carbon products from these high temperature polymer matrices will also be characterized. MODA and BODA are prepared through a Sonogashira coupling reaction and are polymerized through a heat-initiated Bergman Cyclization reaction mechanism. This work seeks to show how BODA-MODA copolymers can attenuate current composite processing limitations, and improve mechanical properties while retaining high temperature properties including high carbon yields.

No description available.

The discovery of nanotubes with unique mechanical, electrical, and thermal properties has led to their use in the development of the next generation of composite materials. However, their poor solubility and dispersion properties in any organic and aqueous solvents limits their potential applications. In order to improve their solubility, single-walled carbon nanotubes (SWNTs) were functionalized along their sidewalls with phenol groups using a 1,3-di^polar cycloaddition reaction. These phenols could be further derivatized with 2-bromoisobutyryl bromide, resulting in the attachment of atom transfer radical polymerization initiators to the sidewalls of the nanotubes. These initiators were found to be active in the polymerization of methyl methacrylate and t-butyl acrylate from the surface of the nanotubes. However, the polymerizations were not controlled, leading to the production of high molecular weight polymeric grafts with relatively large polydispersities. The resulting polymer carrying nanotubes were analyzed by IR, Raman spectroscopy, solid-state NMR, DSC, TEM, and AFM. The nanotubes functionalized with poly(methyl methacrylate) were found to be insoluble in organic solvents, such as THF and CH2CI2. However, the dispersion property of SWNTs in the polymer matrix was improved dramatically. Another monomer t-butyl acrylate (t-BuA) was also polymerized using the same macroinitiators. It was found that the SWNTs functionalized with t-BuA iii were soluble in a variety of organic solvents. The t-butyl groups of these appended polymers could also be removed to produce nanotubes functionalized with poly (acrylic acid), resulting in nanocomposites that are soluble in aqueous solutions. In addition, polystyrene (PS) which was prepared by stable free radical polymerization, was used to functionalize SWNTs through the radical coupling reaction. IR, NMR, TEM, and AFM confirmed that this polystyrene was covalently bonded to the SWNTs. It was also found that the resulting PS-SWNTs composites were quite soluble in organic solvents, such as THF and CH2C12. / Thesis / Master of Science (MSc)

Polymer nanocomposites have been proposed as lightweight replacements for traditional composite materials in various applications. Montmorillonite (MMT) and carbon nanotubes (CNTs) are two nanofillers which have accrued significant interest in the past 20 years due to their superior mechanical and electrical properties, respectively. However, efficient dispersion of the nanofiller and damage to CNTs prevent widespread utilization of these materials in polymer nanocomposites. Novel methods of nanocomposite generation combining the use of supercritical carbon dioxide (scCO2) with melt compounding have been investigated to overcome these issues. The focus of this work is on developing the scCO2 treatment of nanomaterial for thermoplastic nanocomposite generation. First, the supercritical carbon dioxide aided melt blending method was applied to nanoclay nanocomposites of Nylon 6/ and organoclay where the polymer may interact with the nanoclay surface. Second, the effect of scCO2 processing of CNTs was investigated with special consideration to the processing variables. Finally, a study was carried out to analyze the electrical conductivity of polycarbonate nanocomposites generated using CNTs deagglomerated by scCO2 processing. The initial focus of this dissertation is the use of supercritical carbon dioxide (scCO2) as a processing aid in the generation of nylon 6 nanocomposites in which the nylon 6 may interact with the nanoclay surface. Wide-angle X-ray diffraction, transmission electron microscopy, rheology, and tensile tests were carried out to investigate the effect of processing with scCO2 on the final composite morphology and properties. It was observed that mechanical properties of composites prepared with the scCO2 aided melt blending method were similar to or higher than those reported in the literature for samples prepared with twin screw compounding. At 7.6 wt% nanoclay the modulus value reaches 4.75 +/- 0.194 GPa which is one of the highest increases (1.7 GPa) reported for these materials processed at intermediate concentrations. Beyond 7.6 wt% the improvement due to scCO2 processing matched that of direct blending. The next objective of this work is to develop a method for the deagglomeration of commercially available multi-walled carbon nanotubes (MWCNTs) by manipulating processing variables and observing carbon nanotube aspect ratios after deagglomeration. High levels of deagglomeration of Baytubes C 150 P and Nanocyl NC-7000 MWCNT agglomerates were observed, resulting in 30 fold and 50 fold decreases in bulk density, respectively, with median agglomerate sizes < 8 um in diameter. These results were obtained while retaining the aspect ratio of the as-received nanomaterial, irrespective of the MWCNT agglomerate morphology. It was found that the supercritical temperature and pressure of 40 deg C and 7.86 MPa were the optimal temperature and pressure for maximum deagglomeration without damaging the MWCNTs. The final goal of this work is to apply the scCO2 aided melt blending process to generate polycarbonate/ carbon nanotube (CNT) nanocomposites with enhanced electrical conductivity and improved dispersion while maintaining the aspect ratio of the as-received CNTs. Different degrees of scCO2 processed Baytubes C 150 P CNT were benignly deagglomerated with scCO2 resulting in 5 fold (5X), 10X, and 15X decreases in bulk density from the as-received CNTs. The CNT were melt compounded with polycarbonate using single screw melt extrusion and compression molded into plaques. A surface conductivity of 4.8 x 10-8 +/- 2.0 x 10-9 S was observed for samples prepared with the scCO2 aided melt blending at 15X scCO2 processing. Electrical percolation thresholds as low as 0.83 wt% were observed for composites prepared with 15X CNTs using the scCO2 aided melt blending method, while concentrations as high as 1.5% are required without scCO2 processing. The percolation concentration in nanocomposites prepared with 15X scCO2 processing and single screw extrusion is competitive with values reported for similar nanocomposites generated using twin screw melt compounding in the literature. Optical microscopy, transmission electron microscopy, and rheology were used to investigate the dispersion and mechanical network of CNTs in the nanocomposites. The dispersion of CNTs generally improved with scCO2 processing compared to direct melt blending but was found to be significantly worse than that of twin screw melt compounded nanocomposites from the literature. Because the percolation thresholds are similar with substantially different extents of dispersion, the importance of maintaining longer CNTs during nanocomposite generation is emphasized. / Ph. D.

No description available.

Call number: LD2668 .T4 1965 G47 / Master of Science

M. methulotrophus is a Gram negative obligate methylotroph depending on the presence of reduced carbon compounds containing one or more carbon atoms, but containing no carbon-carbon bonds. This organism can synthesize all its cellular constituents from methanol, trimethylamine, dimethylamine, or methylamine. Conversion of methanol and the methylated amines to cell carbon involves the ultimate oxidation to formaldehyde and ammonia. While the methanol dehydrogenase is produced constitutively, the enzymes involved in the assimilation of the methylated amines are inducible. All three enzymes of the trimethylamine pathway are always induced regardless of the methylated amine substrate. Transposon mutagenesis was used to generate mutations in M.methylotrophus and an antibiotic selection procedure used to isolate mutants defective specifically in the trimethylamine pathway. Two mutants were characterised and subjected to further study. The mutant tmd 3 was unable to utilise trimethylamine, dimethylamine or methylamine as substrates and was shown to lack trimethylamine dehydrogenase by polyacrylamide gel electrophoresis. Enzyme studies confirmed the lack of the dehydrogenase within the mutant cells. The mutant mad 1, unable to use methylamine as a substrate, was shown via enzyme studies to contain trimethylamine dehydrogenase, and dimethylamine dehydrogenase, but to lack methylamine dehydrogenase activity. Molecular cloning of wild-type M. methylotrophus DNA in a broad host-range plasmid vector was used to isolate DNA fragments that could replace the mad 1 defect. An 11kb fragment was isolated that fully restored methylamine dehydrogenase activity to mad 1 cells. A 2.5kb fragment was subcloned and shown, by Southern blotting with 32P-labelled In5 DNA as a probe, to contain the site of integration of the In5 insertion, located to within a few hundred base pairs of the end. DNA sequencing, now in progress, has generated 600 base pairs of sequence from either end of the subcloned fragment, within which several regions of interest were noted.

No description available.

This thesis compares 23 anthropogenic charcoal deposits to 19 corresponding control sites, along a European climatic gradient from Temperate Maritime (South Wales) to Mediterranean (southern Italy) environments.