David J. Moreton

Adsorption isotherm and atomic force microscopy studies of the interactions between polymers and surfactants on steel surfaces in hydrocarbon media

The adsorption isotherms for certain polymer and surfactant molecules (and in some cases their mixtures) on stainless steel beads from isooctane have been obtained, together with corresponding adsorbed layer thicknesses, using an atomic force microscope. The polymer is a terminally functionalised (ethylene diamine), low molecular weight polyisobutylene (PIB) derivative and the surfactants are basically alkyl or alkyl phenol alkoxylate molecules, which in one case has been derivatised with an amino functionality. The results indicate the presence of multilayers at the stainless steel-isooctane interface. Theoretical analysis of the surfactant adsorption isotherms suggests molecular aggregation at the interface with an aggregation number between 2 and 6, at the highest coverages. The adsorption of the polymer is reduced in the presence of the surfactant molecules. The polymer leaches metal ions from the steel surface at higher concentrations.

Deposition studies of carbon particles on stainless steel surfaces from hydrocarbon media

Abstract The adsorption isotherms for carbon particles of about 200 nm size, in the presence of various combinations of a terminally functionalised (amine) polyisobutylene polymer and alkylpropoxylate/alkylbutoxylate surfactant molecules, on 7 μm diameter stainless steel beads from isooctane solutions have been obtained. The deposition of carbon particles on stainless steel plates was achieved using a flow-cell and analysed using scanning electron microscopy. The flow-cell was also used to study the “cleaning” properties of various polymer/surfactant solutions, in their ability to remove deposited particles. It was found that the polymer molecules were much more effective dispersants and stabilisers for the carbon particles, but the surfactant molecules were much better at effecting anti-deposition and subsequent removal of deposited carbon particles, and provide carried adsorbed polymer chains.

The Adsorption of Nonionic Surfactants onto Stainless Steel Surfaces from Iso-Octane

The synthesis of nine, nonionic, fuel-soluble poly(isobutylene)-based surfactants, and an assessment of their ability to remove and prevent carbonaceous deposit build up on light-duty vehicle engine valves, is described. Surfactants with varying surfactant head group polarity and structure, and tail length, were assessed for their potential fuel surfactant efficacy by establishing their adsorption kinetics and adsorption isotherms, from iso-octane, onto stainless steel surfaces, using both solution depletion and ellipsometry measurements. Increasing head group polarity from a simple phenol group, by the inclusion of an amine group, increased the adsorption affinity and the maximum adsorbed amount. Inclusion of additional amine groups also increased them maximum adsorbed amount, albeit only marginally. Replacing N-Me groups by N-H groups also increased the adsorbed amounts. Surfactant adsorption was found to be independent of tail length and the maximum adsorbed amount corresponded more-or-less to the surface concentration of strong acid groups on the steel surface, as determined by a Boehm titration. Additionally, all the surfactants studied appeared to adsorb onto the steel surface “irreversibly.”

An Insight into Ion-transport by Calixarenes; the Structure of the Dipotassium Complex of P-tert-butylcalix[8]arene Crystallised from a Protogenic, Coordinating Solvent [ethanol/diethylcarbonate (10:1)]

The structure of the dipotassium complex of the dianion of p-tert-butylcalix[8]arene crystallised from a protogenic, coordinating solvent (ethanol–diethylcarbonate, 10:1) shows that the metal ions are bound above and below the cavity of the calix[8]arene, which adopts a ‘pinched’ conformation.

A mixed lithium–strontium polynuclear complex formed within the hexa-deprotonated calix[8]arene framework; the synthesis and structure of Li4Sr2(H2L)(O2CC4H9)2(dmf)8 [H8L = p-Pri- or p-Bui-calix[8]arene]†

The deprotonation of calix[8]arenes (H8L) with BunLi in DMF followed by reaction with dry SrBr2 yielded the discrete molecular complexes Li4Sr2(H2L)(O2CC4H9)2(dmf)8 (H8L: 1, p-Pri; 2, p-Bui); the crystal structures of these complexes of hexa-deprotonated calix[8]arenes show that mixed metal, polynuclear, inorganic cores can be formed within the large and flexible cavity of calix[8]arenes.