The electron beam induced polymerisation of dialkyltin diacrylates, as well as the UV and electron beam induced polymerisation of some novel silicon containing acrylates are discussed. The reactivity and film forming properties of these materials are compared with that of some commercial diluents such as, tripropyleneglycol diacrylate, TPGDA and trimethylolpropane triacrylate, TMPTA. Mechanistic studies concerning the initiation of free radical polymerisation of the acrylate ester, isodecylacrylate, IDA on electron beam irradiation are presented. Addition of electron and hole scavengers revealed that slow electrons contribute significantly to the initiation of electron beam induced polymerisation of acrylate esters. The film forming properties of phenyl acrylate and mono-, di- and tri- halophenyl acrylates on exposure to electron beam irradiation are evaluated in terms of their ability to produce tackfree films. The sensitivity of catechol diacrylate compared with t-butyl catechol diacrylate is also presented. Mechanistic studies concerning the initiation of both UV and electron beam induced cationic polymerisation of 3,4-epoxycyclohexylmethyl-31,41 -epoxycyclohexanecarboxylate, with the aid of diphenyliodonium hexafýuorophosphate, triphenylsulphonium hexafluorophosphate and (n -2,4-cyclopentadien- I-yl) [(I, 2,3,4,5,6-n) (-I-methylethyl) benzene] -iron(I+) hexafluorophosphate, as well as the radiolysis of 6,7-epoxy- 3,7-dimethyloctylacrylate in the presence of diphenyliodonium hexafluorophosphate are presented. The decomposition of the salts was monitored in situ by infrared and UV spectroscopy and hydrogen fluoride is credited as the true initiator of the cationic polymerisation of epoxides in an open system. The UV photolysis of the aforementioned onium salts led to the production of volatiles, resulting in the polymerisation of thin films of 3,4-epoxycyclohexylmethyl-31,41 - epoxycyclohexanecarboxylate, providing further evidence of hydrogen fluoride evolution. The use of FTIR- photoacoustic spectroscopy was proven to be an invaluable tool in monitoring the polymerisation of thin epoxide or acrylate films on an opaque substrate.

Lyoluminescence (LL) of the phosphors glutamine and mannose was used to determine instrument stability, reproducibility of readings, sensitivity and lowest detectable dose in order to evaluate the performance of the Aberdeen LL Research Reader (before and after modifications) and compare it with commercially available luminometers. The dependence of the LL yield on mass of dissolved glutamine, the sample's irradiation temperature, and solvent temperature were investigated and correction factors determined. Heat treatment was found to remove the dependence on pre- and post-irradiation storage time. Using aqueous LL dosimetry of glutamine, unknown doses in the range 10Gy to 3kGy were determined with overall accuracy and precision of 2% and 5% respectively during the 1982 IAEA Dose Intercomparison trials. Factors affecting the LL of mannose in water and methanol were compared, and a 20-fold increase in LL yield was reported using the latter solvent. Various attempts to enhance the LL yield from glutamine and mannose were made: Enhancements, of up to 10⁵ times, caused by the oxidation of luminol, lucigenin, lophine and trichlorophenol oxalate by the primary species in LL were observed, but increased background readings due to self-glow caused there to be no advantage in overall sensitivity. Enhancement factors (EF) up to 100 were obtained using glutamine LL in free and chelated rare earth ion solutions, as a result of intermolecular energy transfer from excited organic molecules in solution. However, the enhancement was found to be dose dependent. By employing dibromoanthracene sulphonate, rubrene, eosin and reduced lucigenin, all of which respond to singlet oxygen, EF of up to 10 were achieved in LL of mannose. Finally, as the use of aqueous solutions was found to severely limit the possible phosphor/enhancer combinations, the LL of some carboxylic acids in alcoholic media was investigated. These were found to be less sensitive LL phosphors than either mannose or glutamine.

No description available.

No description available.

The primary photochemical processes of lignin-rich high-yield thermomechanical pulp (TMP) have been investigated with a view to understanding and ultimately preventing the yellowing (photoreversion) of such paper upon exposure to sunlight. This would enable their use in longer-life paper products and therefore represent large raw material and cost savings to the pulp and paper manufacturer.

Naphthoxazine-spiro-indolines (NOSIs) can exist in a colourless and a coloured form. These compounds can interconvert between these two forms either photochemically or thermally and are resilient to degradation even after repeated cycles of colouration and bleaching. Absorption spectra of both the stable colourless form and the energetically less stable coloured form have been measured. Several NOSI compounds have been shown to photoconvert to the coloured form with an efficiency of between 0.06–0.74, depending upon the compound conditions under which the conversion is brought about. The factors which have been varied in this work are: the basicity of the 6'-substituent; the size of the N-alkyl group within these compounds; and the nature solvent or matrix in which the reaction occurs. Electron donation from the 6'-group has been shown to increase the quantum yield of the forward reaction whereas solvent polarity increases have been shown to reduce the quantum yield.

This thesis is concerned with the preparation of regiospecifically labelled compounds by homogeneous metal catalysed hydrogen isotope exchange reactions. The features of homogeneous hydrogen isotope exchange reactions are discussed in Chapter 1, along with other exchange methods; acid, base, heterogenous metal, radiation, enzymic and zeolite catalysis. In Chapter 2, homogeneous rhodium trichloride is investigated for regiospecificity of tritium labeling in a wide range of aromatic compounds. High regiospecificity of labelling ortho to carboxyl, carboxamide and methanamide groups is found, with the regiospecificity determined by 3H nmr spectroscopy. Also discussed is a study to determine whether any other Group VIII metal complexes will catalyse the ortho tritiation of benzoic acid, in addition to rhodium trichloride. The results of detritiation studies performed on benzoic acids using ruthenium acetylacetonate as catalyst as a model for rhodium trichloride are presented in Chapter 3, A possible reaction mechanism is also presented. Finally, an application of the rhodium trichloride system to the labelling of biologically useful molecules is discussed in Chapter 4. The deuteration and tritiation of a number of drugs and metabolites containing known ortho directing groups is described. In a large number of cases, the regiospecificity for ortho labelling is very high.

The effects of a range of complexing agents on the radiation damage routes in frozen aqueous DNA have been analyzed by ESR techniques in a semi-quantitative way. Establishment of additive-free DNA standards for this study revealed an ESR pattern different from the four elementary shapes which contributed ∼ 13X of the total spin seen after annealing to 210 K. It is proposed that this represents a population of sugar radicals; hitherto unseen intermediates in additive-free systems between secondary base radicals and strand breaks. The intercalating aminoanthraquinones, mitoxantrone and ametantrone, were found to compete very efficiently with thymine for electron capture, and behaved as protecting agents. Concomitant strand break studies did not support this, and more extensive ESR studies suggested that the intercalator radical centre could also lead to strand breaks. It is therefore proposed that the mode of action of these drugs does not involve free radical processes in DNA. Use of these agents provided evidence that electron migra tion in DNA is much more extensive than previously thought. Copper ions were found to reduce the amounts of T/TH detected, with no effect on G . During this evaluation, evidence appeared for the existence of a site on DNA that could bind two Cu(II) ions so close together that they became ESR silent. Of special interest was the finding that this binding was preferred over that of single Cu(II) ions, and it is proposed that this might have a physiological significance. The dominance of thymine over cytosine as the site of electron capture is reinforced by the above studies, but it is suggested that it is the nature of the system under study that determines the ratio of T to C.

This thesis is concerned with a process which has become commonly used. Producing radical cations specifically for observation at reduced temperatures within the X-band electron spin resonance spectrometer cavity. Gamma irradiation is used to cause electron addition and electron loss centres in a CCl3F matrix. These damage centres can be passed to solutes by the processes outlined below:- [equation] Various functional groups have been investigated. A variety of groups have been chosen to attempt to show a great many of the effects, which cause a molecule to produce interesting e.s.r. spectra. Effects ranging from the 'solvent adducts' investigated in Chapter 2, to the Breit-Rabi distortions encountered by the cations of dialkyl mercurials. Attempts have also been made to clarify one or two areas of radical cation chemistry which have caused contention in the current literature. Such areas are those outlined in Chapters 3, 4 and 5 with ester groupings and Chapter 7 with oxirane cations.

Lors d’un Accident Grave (AG) survenant à un réacteur nucléaire à eau pressurisée, sous atmosphère fortement oxydante, des relâchements importants de ruthénium, depuis le combustible dégradé, sont attendus du fait de la formation d’oxydes gazeux. Les composés de Ru représentent un risque sanitaire lié aux isotopes 103Ru et 106Ru, radio-contaminants à court et moyen terme. En outre l’oxyde RuO4, volatil à température ambiante, est susceptible d’être relâché à l’environnement via les fuites de l’enceinte de confinement. L’évaluation de ce rejet à l’environnement présente des incertitudes importantes, liées entre autres aux données thermochimiques des composés de ruthénium gazeux avec des disparités entre les valeurs de la littérature pour les oxydes. Concernant les oxyhydroxydes, les données sont très parcellaires et celles disponibles sont sujettes à caution. Une première étape de ces travaux de thèse a consisté au développement d’une méthodologie de calcul pour obtenir les données thermochimiques des oxydes de ruthénium gazeux en fonction de la température, via des outils de chimie quantique, avec la fonctionnelle TPSSh-5%HF pour l’optimisation de géométrie, suivi de la méthode CCSD(T) pour le calcul des énergies électroniques. Cette méthodologie fut ensuite étendue aux oxyhydroxydes. Des calculs de spéciation chimique ont été effectués afin de prédire les espèces gazeuses les plus stables lors d’un AG. A l’aide des propriétés thermochimiques des espèces d’intérêts et des méthodologies développées, une étude cinétique a été conduite afin de déterminer les chemins réactionnels conduisant à la formation d’oxydes de Ru, espèces gazeuses les plus stables en conditions AG. / During a severe accident (SA) occurring to a pressurized water reactor (PWR), fission products (FPs) are released from the nuclear fuel and may reach the nuclear containment building. Among the FPs, ruthenium (Ru) is of particular interest due to its ability to form volatile oxide compounds in highly oxidizing conditions combined with its high radiotoxicity (103Ru and 106Ru isotopes) at middle term after the accident. Uncertainties concerning evaluation releases of Ru are important and some R&D efforts are led to get a better understanding of ruthenium chemistry in such conditions. The thermodynamic database on ruthenium species used to estimate these releases shows some discrepancies for most ruthenium oxides and for other species such as oxyhydroxides, data are scarce and not reliable, calling for quantum chemical calculations. The most suitable approach corresponds to TPSSh-5%HF for geometry optimization, followed by CCSD(T) for the calculation of the total electronic energies. The energetics are combined with statistical physics to obtain the thermochemical properties of ruthenium oxides and ruthenium oxyhydroxide species as the latter may play an important role on the transport of ruthenium in the primary circuit due to high steam content. The revised thermodynamic database is then used to predict which species are most stable in representative severe accident conditions. Next, kinetic calculations are also performed to obtain pathways of formations for ruthenium trioxide and tetraoxide gaseous compounds, which are the most stable Ru volatile species in steam/air atmospheres.