Browsing by Author "Cooper, W. David"

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Calculation of Dispersion Force Interactions Between Colloidal Particles in Butan-l-ol
(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1978, 74 (08), 1978) Cooper, W. David; Marsden, Robert S.
Calculation of dispersion force interactions between colloidal particles of Graphon, polystyrene and polytetrafluoroethylene dispersed in butan-1-ol using the Lifshitz method is described. The complex frequency-dependent permittivity has been estimated from spectroscopic data for the colloidal materials and has been used to assess the frequency dependent contributions to the Hamaker function over a range of particle separation distances. The Hamaker functions for interaction between Graphon particles, and between Graphon and polystyrene particles are shown to be insensitive to the precise value of the static permittivity of Graphon. In contrast the dispersion force interaction between Graphon and PTFE is markedly dependent on the value of Îµ0(Graphon) and may under some conditions be repulsive.
Colloid Stability in Butanol
(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1978, 74 (09-12), 1978) Cooper, W. David; Marsden, Robert S.
The stability ratio (W) of colloidal dispersions of Graphon and polystyrene dispersed in butanol containing varying amounts of HCl and LiCl has been determined. Rate constants for rapid flocculation are found to be in good agreement with the predictions of Smoluchowski. The dependence of W on zeta potential for G and PS have been compared with the predictions of theory.
Electrophoresis of Colloidal Copper Phthalocyanines in Low Permittivity Liquids
(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1974, 70 (1-6), 1974) Cooper, W. David; Wright, Paul
The electrophoretic behaviour of colloidal β-copper phthalocyanine and monochloro substituted α-copper phthalocyanine dispersed in heptane and benzene has been investigated. Changes in zeta potential with concentration of anionic (Aerosol OT) and cationic [di-(2-ethylhexyl)ammonium chloride] surfactant, and the surfactant adsorption isotherm have been determined. In addition, the effects on the electrophoretic mobility of the polar additives water and methanol have been examined. It is suggested that the zeta potential in the presence of small amounts of polar additives is primarily determined by the extent of counter ion penetration into the inner regions of the double layer. In consequence it may be invalid to approximate the surface potential to the zeta potential in systems of this type.
Origin of Charge on Colloidal Particles in Butanol
(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1978, 74 (06), 1978) Cooper, W. David; Marsden, Robert S.
The electrophoretic mobilities of colloidal polystyrene, polytetrafluoroethylene and the carbon blacks Graphon and Black Pearls A dispersed in butanol have been determined. From changes in electrophoretic mobility caused by additions of H2O, HCl and LiCl it is deduced that the fundamental particle charging mechanism involves proton transfer. Water appears to have no major effects other than those resulting from its acidity with respect to butanol. The variation of electrophoretic mobility with increase in electrolyte concentration follows the trends indicated by electrical double layer theory.