No description available.

This thesis describes a set of experiments to investigate the properties of fully relaxed reactions in the mass 80 region. Symmetric and asymmetric entrance channels, leading to similar compound nuclei, have been compared in order to determine the characteristics of the reaction mechanism. The symmetric system ⁴⁰Ca + ⁴⁰Ca has been studied at laboratory energies of 197.3 and 230.5 MeV. The fissionlike products were detected by a series of six time of flight telescopes, placed at angles between 10° and 52.4° to the beam, and a Bragg curve spectrometer-multiwire proportional chamber telescope, situated at 30°. Data were collected in both singles and coincidence modes. To complement this measurement, fully damped yields from ²⁸Si + ^50,52,54 Cr at 130 MeV and from ²⁸Si + ⁵⁰Cr at 150 MeV were measured using an array of four avalanche counter-silicon surface barrier detector telescopes spanning the angular range between 20° and 50°. The avalanche counters used in this experiment are of a new design which was developed in Oxford. We present the features of this design and discuss the detectors' operational characteristics. Several possible interpretations of the data are considered. It is shown that diffusion models of deep-inelastic scattering tend to underpredict the measured fully relaxed cross sections. Rotating finite range model calculations of fission barriers point to the possibility of fast-fission in this mass region; a process hitherto associated with much heavier systems. Furthermore, such models also predict that these systems may fission asymmetrically. The more commonly employed rotating liquid drop model of the nucleus is unable to predict either of these effects. The data are compared with those reported in the literature for other systems in this mass region. It is argued that all these results are consistent with fast-fission and asymmetric fission, thus obviating the need for the previously proposed interpretation in terms of intermediate mechanisms.

No description available.

No description available.

The purpose of this research was to synthesize a novel crown ether compound that has been designed to fluoresce with greatly enhanced intensities when in the presence of selected alkali metal cations. The novel crown ether compound (cryptand) 12,25-(1,5 - dimethyloxynaphtho)-1,4,7,10,14,17,20,23-octaoxacyclohexacosane (1) was synthesized through 6 steps. The general synthetic route for the preparation of cryptand 1 is given in the proposed synthetic procedure. Reaction of benzaldehyde (23) with glycerol (24) in the presence of concentrated sulfuric acid afforded cis and traps-1,3-O-benzylideneglycerol (25). Cis and trans-2-O-benzyl-1,3-O-benzylideneglycerol (27) was obtained when 1,3O-benzylideneglycerol (25) was treated with benzyl bromide (26) and sodium wire in benzene. Acid-hydrolysis of the 2-O-benzyl-1,3-O-benzylideneglycerol (27) in methanol gave 2-O-benzylglcerol (28). The key starting material is 12,25-bisbenzyloxy1,4,7,10,14,17,20,23-octaoxacyclohexacosane (31), which requires the formation of four carbon-oxygen bonds. 2-O-benzylglcerol (28) was reacted with triethyene glycol ditosylate and sodium hydride in dioxane. This treatment gave the product 12,25-bisbenzyloxy1,4,7,10,14,17,20,23-octaoxacyclohexacosane likely to be (31) along with the 1:1 and a 3:3 crown ether products. The compound likely to be (31) was treated with H2 and a Pd/Ccatalyst and the resulting compound was 12,25-dihydroxy-1,4,7,10,14,17,20,23Octaoxacyclohexacosane (2). Compound likely to be (2) was reacted with 1,5bis(bromomethy)naphthalene and potassium t-butoxide in tetrahydrofuran to give the final cryptand compound 1. The structures of the crown ethers, the products of this reaction, have not yet been unambiguously assigned. / Department of Chemistry

No description available.

Several systems, containing up to 10 mol % ionic co-units, were investigated by dynamic mechanical techniques, primarily above the glass transition. The ionic units in quaternized poly(styrene-co-4-vinylpyridine) mildly retard chain diffusion. In contrast, the rubbery plateau of blends of poly(styrene-co-styrene-sulfonic acid) and poly(ethyl acrylate-co-4-vinylpyridine), compatible above ca. 4 mol % co-unit content, is greatly extended, independent of co-unit content. It is postulated that the kinetics of ion dissociation and reassociation in the blends are faster than chain diffusion, effectively trapping chain entanglements for comparatively long times. Time-temperature reducibility applies to both the cationic ionomers and the blends. It fails at high plasticizer contents for poly(styrene-co-sodium methacrylate), of 5 mol % ion content, plasticized by a styrene oligomer. Two relaxation processes are evident in this system. Nonpolar diluents plasticize the ionic regions of carboxylated more than sulfonated ionomers. Polar diluents destroy the effect of ionic associations in the transition and rubbery zones.

Reprints of five arricles by the author bound in at back of volume / iv, 201 leaves : ill. ; 27 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Organic Chemistry, 1974

Since their discovery in the late 1970s conducting polymers have become increasingly used materials in many applications. They are utilised for their conductivity and/or their electroactive properties. These applications include sensor technologies, actuators, and battery materials. The properties of conducting polymers rely on the extent of the reduction / oxidation or redox state, and hence the dopant levels, of the materials. The aim of this work was to investigate the use of the Ion Beam Analysis (IBA) techniques Rutherford Backscattering Spectroscopy (RBS), and Proton Induced X-ray Emission (PIXE) for the analysis of 'soft' organic materials, in particular, conducting polymers. These IBA techniques are not new, as they have been extensively used for the characterisation of many inorganic, 'hard', materials such as aluminium oxide and silicon oxynitride. While they have been used to alter the molecular structure, and hence the properties of conducting polymers in the past, little to no research has explored the use of ion beams as a tool for the characterisation of these materials. Conducting polymers can either be prepared chemically or electrochemically. They are predominantly prepared in an oxidised state and this charge is balanced by negatively charged counter ions. In this work, the conducting polymers were formed electrochemically by deposition onto support materials at constant electrode potential. The number of counter ions required to balance the polymer chain depends on the type of conducting polymer formed and extent of oxidation. Issues such as the influence of the support material and extent of polymer oxidation on the extent of counter ions through the polymer films are of importance. Gaining knowledge of the dispersion of counter ions may provide new insights into the redox mechanisms for conductive polymers. Complex bis terthiophene porphyrin conducting polymers were prepared and investigated for the uptake of zinc into the freebase porphyrin unit after polymerisation by acquiring elemental depth profiles using RBS analysis. Issues such as the influence of the support material and extent of polymer oxidation on the extent of counter ions through the polymer films were found to be of importance. Gaining knowledge of the extent of counter ions provides new insights into the redox mechanisms for conductive polymers. The results were compared to those obtained for a sample where zinc was coordinated to the porphyrin prior to the polymerisation process. Unexpected high concentrations of both nitrogen and oxygen were found, which were interpreted to be due to entrapped cations originating from the electrolyte ((Bu)4N+), together with trapped water molecules, within the polymer films. The chlorine depth profiling assisted with understanding the extent of the perchlorate counter ion throughout the polymer films. The combination of both RBS and PIXE demonstrated that trace element impurities can be detected using ion beam analysis, which other analytical techniques are unable to do. A series of polypyrrole films incorporating a range of counter ions were prepared as model compounds for study in the second section of this work. RBS and PIXE techniques were used to evaluate film homogeneity with respect to depth and to infer the counter ion / pyrrole unit ratio for each of the six PPy film formed. RBS was also used to characterise a series of terthiophene-ferrocene based conducting co-polymers. The ratio of co-polymer monomer to terthiophene-ferrocene monomers and the dopant levels for the polymers were determined using a RBS deconvolution method developed in this study. This new method can be extended for characterization of a wide range of organic polymers. The limitations of RBS for the analysis of these soft materials were identified. The advantage that RBS offers over other analytical techniques is that it provides a means for low atomic number element depth profiling in these materials.

Thesis (M.S.) in Chemistry--University of Maine, 2007. / Includes vita. Includes bibliographical references (leaves 92-99).