This thesis reports a study of adsorption of small molecules by macromolecules and the deaggregation of micelles in aqueous solution. These phenomena were investigated using an isothermal titration microcalorimeter. Procedures are described for the analysis of enthalpograms which characterise the adsorption of anionic surfactants, sodium dodecylsulphate (aq), copper dodecylsulphate(aq) and sodium decylsulphate(aq) by a water soluble polymer Poly (N-vinlypyrrolidone)PVP(aq). The application of equations based on both Langmuir and Frumkin adsorption isotherms are discussed. Characteristics features of the enthalpograms for the adsorption are described using equations developed from the Frumkin equation. The adsorption was endothermic as a consequence of hydrophobic interactions between polymer and surfactant. The analysis describes absorbate-absorbate interactions using enthalpic interaction parameters. Critical micelle concentrations (cmc) of copper, cadmium and nickel dodecylsulphate(aq) in aqueous solution were measured. The calorimetric plots showed an extrema which corresponded to the cmc which was in close agreement with literature values based on surface tension measurements. Enthalpograms for deaggregation of micelles formed by alkyl trimethylammonium bromide surfactants were classified into three types, A, B, and C. The classification is based on the shape of the plot of the enthalpy of dilution as a function of surfactant concentration. The effect of the cmc and the enthalpogram of added benzoates to n-hexadecyltrimethylammonium bromide(aq) was investigated. The cmc was reduced and the classification changed from Type A to Type B in all cases. This pattern was accounted for in terms of adsorption of benzoate ions into the Stern layer of the micelles.

This thesis describes a study of the bubble evolution mechanisms of four systems; H2/HC1O4Au, H2/HCIO4/Pt, Cl2/NaCl/RTO and Cl2/NaCl/Ti as a function of current density, surface composition (RTO) and morphology. Three experimental techniques have been used, fast frame video (FFV), electrochemical quartz crystal microbalance (EQCM) and the pressure release bubble nucleation technique (PRBN). The three complementary techniques were utilised to provide a comprehensive study of bubble behaviour. The FFV was used to study individual bubbles, the EQCM to measure the detachment rate integrated over the nucleating surface area, and the PRBN technique was used to measure the bubble nucleation rate integrated over space and time. In the current density range 3-44 mA cm-2 nucleation of individual hydrogen bubbles was found to be rapid at vertical gold and platinum electrodes. For both electrode materials, the detachment radius decreased as a function of current density, but the average bubble size on detachment was approximately 50% smaller on the platinum electrode. The detachment rate and number of active nucleation sites both increased as a function of current density, and the dominant detachment mechanism was coalescence between closely paired neighbouring bubbles. EQCM analysis of the overall detachment rates at the electrodes confirmed the visual observations; novel Fast Fourier Transform analysis of the frequency response from the gold electrode showed that the detachment frequency increased with current density, but there was little change in the volume of gas resident on the electrode. On the platinum electrode small bubbles detached rapidly and were characterised by small fluctuations in the EQCM resonant frequency response. Using the FFV technique, nucleation was found to be the rate-limiting step for chlorine bubble evolution at an RTO electrode in the current density range 18-56 mA cm-2.

The chemical reactivity of the halogenoalkylsilicon compounds has been reviewed and the published quantitative work on the decomposition of 2-halogenoalkylsilicon compounds outlined. The gas phase thermal decomposition of 2--chloroethyltrichloro-silane has been investigated in a static system between 356 and 417C at initial pressures of 12 - 138 mm. Hg. Use has been made of pressure measurement, gas chromatography and mass spectrometry to obtain kinetic data and to establish the mechanism of the reaction. The over-all reaction scheme is, 1. ClCH2CH2SiCl3 [right arrow] CH2=CH2+ SiCl4, 2. ClCH2CH2SiCl3 [right arrow] CH2=CH.SiCl3+HCl 3. ClCH2CH2SiCl3 [right arrow] CH2=CHCl+ HSiCl3, 4. CH2=CHCl + HSiCl3 [right arrow] CH2=CH.SiCl3+HCl, 5. CH2=CH2 + HSiCl3 [right arrow] CH3.CH2.SiCl3 where ethylene and silicon tetrachloride account for 72% of the reaction products. A brief study of the subsidiary reactions, 4 and 5, has been made and approximate kinetic data obtained. These reactions are suppressed by nitric oxide and cyclohexene. Reactions 1, 2 and 3 are shown to be simultaneous unimolecular eliminations and the Arrhenius equation for the major reaction, ethylene elimination, is: k1 (Sec.-1) = 1011.26+0.16 e-45,5000+500/RT The low pre-exponential term corresponds to ?S1 = -8.0+0.7 e.u., which suggests a cyclic transition state. In particular, a "quasiheterolytic" transition state may be involved, as in the thermal decomposition of alkyl halides and carboxylic esters, and this possibility is discussed, although accurate correlation cannot be made until more results are available on other 2-halogenoalkylsilicon compounds. An analogous study has been carried out on 2-chloroeth1-dimethlphenylsilane between 236 and 390C. It has been shown that the reaction, ClCH2CH2SiMe2Ph [right arrow] CH2=CH2 + ClSiMe2Ph accounts for more than 99% of the reaction products. However, the reaction is very sensitive to surface condition and it was not found possible to isolate the homogeneous decomposition. Suggestions for resolving this difficulty are made.

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