This work has used laser light scattering to investigate the possible existence of inhonogeneities and other defects in an epoxy resin system, and the role these defects play in the mechanical and electrical failure of the polymer. Mie Theory was used in the analysis of the data throughout this thesis. Ultra clean fully degassed samples were prepared to ensure any scatterers observed were Inherent to the sample. It was discovered that inhomogeneities and microvoids do exist in the fully cured and degassed ultra clean samples before stressing. Reproducible trends in inhomogeneity behaviour were observed on stressing, and a three phase model of inhomogeneity has been proposed to explain this behaviour. This consists of a densely crossllnked core of mainly diester crosslinks, surrounded by a less densely crosslinked network containing more ether crosslinks. These regions are then interconnected by a weaker even less densely crossllnked matrix where it is proposed that initial yield occurs followed by eventual failure. Voids present in the network were observed to grow in a similar manner under both mechanical and electrical stress. This suggests a possible link in the deformation processes under either stress. On release of both types of stress, relaxation occurred and the voids reduced in size although some hysteresis was observed. One distribution of voids reached a plateau in size with applied electrical and mechanical stress and this suggests that not all defects have the potential to cause failure. No wholly reproducible trends were observed for the samples that underwent electrical stress. A common observation was a step type of behaviour that occurred on the release of stress, and also during stressing around a field value of 2.0 x 10[to the power of]6 kV m[to the power of]-1. The later has been attributed to failure occurring at the pin tip epoxy interface causing relaxation in the scattering volume. The overall behaviour with applied stressed varied from sample to sample and has been attributed to complicated mechanical and electrical forces present and the remoteness of the scattering volume from the pin tip. The scattering volume, however is very much affected by what is occurring at the pin tip. It is concluded that the defects present in the epoxy resin do play an important role in the deformation and failure of the polymer. The defomation process under both electrical and mechanical stress are thought to be the same and the deformation under electrical stress results from the mechanical force associated with the electric field.

Nuclear Magnetic Resonance (nmr) spectroscopy has been employed to determine molecular geometries, anisotropies in the indirect spin-spin couplings and chemical shifts, quadrupolar coupling constant, signs of indirect spin-spin coupling constants and conformational preferences of selected molecules by using isotropic and oriented solvents.

The work presented in this thesis has involved an investigation of the thermal decomposition of the Michaelis-Arbuzov intermediates (PhO)3PMeBr, (PhO)3PMeI, (o-CH3C6H40)3PMeBr, and (o-CH3C6H40)3PMeI, in the solid state and in deuterochloroform.

Reactions of highly hindered phosphorus (III) esters derived from 2,2,2-triphenylethanol, 2,2-diethylbutan-1-o1, and norbornan -1-o1 with electrophilic reagents, in particular, α-haloketones were studied by P and pH spectroscopy.

The synthesis of the complexes Cr(1-nqo)3, Cr(2-nqo)3, Cr(3-Me-5-OHqo)3, Cr(6-Me-5-OHqo)3, Mn(1-nqo)3, Mn(2-nqo)3, Mn(1-nqo)2, and Mn(2-nqo)2, has been systematically examined.

The electrochemical reduction of a series of quaternary phenacyclammonium and tertiary phenacylsulphonium salts in aqueous solution at a mercury cathode has been investigated using polarography, coulometry, titrimetry and product analysis methods.

In this work a number of yeast species were assessed for their potential in testing putative toxic and genotoxic compounds. Carbon tetrachloride (CCÍ4) was used as a model compound. Exposure of cells of Schizosaccharomyces pombe and Saccharomyces cerevisiae to carbon tetrachloride showed that the compound was toxic to the cells in a dose-dependent manner. Sch. pombe was more sensitive to the effects of carbon tetrachloride than S. -cerevisiae. Administration of the anti-oxidant a-tocopherot (vitamin E) to ceils of Sch, pombe treated with a toxic dose of carbon tetrachloride appeared to increase cell survival. Thèse data are consistent with work carried out on mammalian cells, and indicate that the toxic effects of carbon tetrachloride are brought about via the generation of free-radical species. Investigation of the genotoxicity of carbon tetrachloride in Sch. pombe and S. cerevisiae revealed that the compound induced mutations to chloramphenicol resistance at concentrations which were toxic to the cells. Carbon tetrachloride also induced forward mutations in Sch. pombe ade6. Genetic analysis of chloramphenicol resistant mutants indicated non-Mendelian inheritance. The drug-metabolising enzyme cytochrome P450 is thought to metabolise carbon tetrachloride to toxic species. The ability of carbon tetrachloride to act as a substrate for the haemoprotein was indicated by the type 1 binding spectrum produced in Sch. pombe. a-Tocopherol was found to increase levels of cytochrome P450. The production of cytochrome P450 was investigated in the three yeast species Sch. pombe, S. cerevisiae and Candida parapsitosis. The enzyme was optimally produced under conditions of glucose repression during the late logarithmic phase of growth. Levels of the enzyme were consistently found to be greater in respiratory deficient (petite) mutants of the yeast S. cerevisiae than in wild type strains. The enzyme was isolated from microsomal preparations of C. parapsilosis. SDS-PAGE analysis revealed a major band in the solubilised fraction possessing a molecular mass of approximately 48 kDa which was tentatively identified as cytochrome P450.

Thallium-205 chemical shifts have been determined for organothallium(III) derivatives RTlx2 and R2TlX (R = alkyl alicyclic, alkenyl,aryl ; X = anion). ... Twenty four new organothallium(III) derivatives have been synthesised and a number of existing syntheses modified.

The protonation end complexetion behaviour of the a-aminomethylenephosphonic acids diethylaminomethylenephonosphonic acid (DEAMPH2), N-ethyliminobis(methylenephosphonic acid) (NEIBMPH4), (+-)-trans-l,2-diaminecyclohexane tetrakis(methylenephosphonic acid) (CDTMPN8) and 5,8-dioxadodecane-1,12-diaminetetrakis(methylenephosphonic acid) (DDDTMPH8) were studied by potentiometry and near spectroscopy.

The synthesis and structure of 1,2-quinone mono-oximes have been reviewed. The reaction of 3-hydroxyphenol, 3-hydroxy-2-aethylphenol, 3-hydroxy-5-methylphenol and N-acetyl-3-aminophenol with amyl nitrite/M(OEt) (M - Na or K) has been systematically examined. It has been found that the complex formed depends on the reaction temperature and phenol/M(OEt) ratio. Infra-red spectroscopic studies have shown that in the solid state 5-hydroxy-l,2-benzoquinone 2-oxime (hqoH,), 5-hydroxy-3-methyl-l,2-benzoquinone 2-oxime (3-MehqoH2), 5-hydroxy-6-methyl-l,2-benzoquinone 2-oxime (e-MehqoH,) and H-acetyl-5-amino- 1,2-benzoquinone 2-oxime (N-AcqoH) and their sodium and potassium complexes exist in the oximic form rather than the nitroso form. Nuclear magnetic resonance studies have also shown that in d,-DHSO solution hqoH,, 3-MehqoH, and 6-MehqoH} and their sodium complexes exist in one form only which is oximic in character. However, in DjO the results for the sodium complexes of hqoH, and e-MeqoH, indicate the presence of at least two species. In the case of the sodium 5-hydroxy-6-methyl-l,2-benzoquinone 2-oximate these species are oximic in character. An X-ray crystallographic study of e-HehqoH, has shown that in the solid state this compound exists in the 1,4- rather than the 1,2-quinone 2-oxlmic form. The synthesis of iron(II) complexes of hqoH,, 3-MehqoH] and 6-HehqoH] using the direct and the nitrosation methods was examined. The direct method gave rise to the complexes Fe(hqoH), OHjO, Fe(3-HehqoH), and Fe(6-MehqoH)2 '2H20 whereas the nitrosation method gave rise to ill-defined solids. Na[Fe(N-Acqo), ]-4H20 was obtained by nitrosation of N-acetyl-3-aminopnenol in the presence of Iron(II) ammonium sulphate. Hossbauer and magnetic studies indicate that Na[Fe(N-Acqo)j]-4H20 is a low spin iron(II) complex whereas the bischelates have properties indicative of the S - 1 spin state. In-vlvo assesment of the iron chelating ability of hqoHj, 3-MehqoH2, 6-MehqoH2, N-AcqoH , N,N-dimethyl-5- amino-1,2-benzoquinone 2-oxime and violuric acid was carried out using a normal rat model. The chelators hqoH, and 6-HehqoH2were found to be effective in removing iron when administered intra-muscularly but they also caused the excretion of magnesium. Their activity was lower than that of desferrioxamine and neither was effective when administered orally.