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The interfacial behaviour of two amphiphillic poly iso-butenyl succinic anhydride (PIBSA)-derived surfactants and the effect of their interaction with various nitrate salts on the stability of a water-in-oil type emulsion has been investigated. The adsorption of the esterification product of PIBSA and coco-diethanolamide (PICDEA) and of Experse-70 (E-70) at the equilibrated aqueous-fuel oil interface was investigated via the measurement of interfacial tension using the ring detachment method.The interfacial pressure of PICDEA decreased in the presence of excess unreacted coco-diethanolamide (CDE) and for both PICDEA and E-70 interfacial pressure decreased with an increase in the length of the poly iso-butenyl (PIB) hydrocarbon tail. Interfacial tension-concentration curves and the Gibbs Equation were used to determine surfactant surface excess concentration and the packing efficiency of the surfactant in the interphase. The double hydrocarbon PICDEA molecule was found to occupy a larger interfacial area than the single hydrocarbon E-70 molecule. The pH of the aqueous phase effects the interfacial activity and nature of, PICDEA and E-70 at the interface. PICDEA is protonated at pH values less than 4.6 and deprotonated at higher pH values. E-70 is neutral at low pH and deprotonated at pH values greater than approximately 2.The effect of sodium, calcium and ferric nitrate salts on the interfacial free energy of the surfactant saturated interface was also determined. The interfacial tension at the E-70 aqueous nitrate interface was dependent on ionic strength alone with a general decrease in interfacial free energy as nitrate concentration was increased. In the case of PICDEA, however, a surfactant-cation orientation effect was observed. The divalent Ca2+ cation attracts two adjacent PICDEA anions resulting in the adverse interaction of hydrocarbon tails in the interphase. This produces an interface with a higher than expected interfacial free energy. The Na+ cation produces an interface with a more energetically stable orientation. PICDEA in the presence of a ferric nitrate solution (pH 1 to 2) is protonated and therefore the univalent nitrate anion forms the counterion layer at the positively charged surfactant interface. Stability studies were carried out on aqueous nitrate salt in diesel emulsions using PICDEA as the stabilizing surfactant. Droplet coalescence rates were determined from droplet size distribution data in the presence of varying concentrations of sodium, calcium and ferric nitrate salts. Droplets were sized microscopically at progressive time intervals and the rate of coalescence determined from the change in droplet concentration with time. Coalescence was found to follow two or more consecutive first order reactions. After an initial period of rapid droplet coalescence, involving small droplets with diameters of 5~m and less, a droplet distribution is attained conducive to a more stable emulsion which then undergoes a slower rate of coalescence involving larger droplets. The effect of the nitrate salt type on the initial droplet coalescence rate (in order of increasing rate) is as follows: Ca2+< Na+< Fe3+. The opposite trend was observed for the slower long term rate of coalescence, i.e. Fe3+< Na+< Ca2+. These trends are explained in terms of the surfactant cation orientation effect, the effect of the droplet's radius of curvature on the potential energy barrier against coalescence and the effect of the droplet distribution of the emulsion system. / Thesis (M.Sc.)-University of Natal, Durban, 1990.

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A dissertation submitted to the Faculty of Science, University of the Witwatersrand, in fulfilment of the requirement for the degree Master of Science (MSc) in Chemistry. Johannesburg, March 2017. / A series of [Pt(diimine)(Ln-O,S)]Cl complexes, where Ln-O,S represents a series of N,N dialkyl-N’-acylthiourea ligands and diimine represents (1,10-Phenanthroline; 5,6-dimethyl 1,10-phenanthroline or [3,2-d:2’,3’-f]-quinoxaline were successfully synthesised and characterised. A new crystal structure was obtained for N,N-di(2-hydroxy)-N’ benzoylthiourea which revealed an interesting herringbone crystal packing arrangement. The cytotoxicity of the series of complexes was evaluated on H1975 lung cancer cell lines at 50 µM and 5 µM. All the complexes were highly cytotoxic with cell death of 90-98% at 50 µM. However, at 5 µM there were much more variations on cell viability percentages. Although the structure–activity relationship can only be established when the IC50 (the concentration of an inhibitor where the response is reduced by half) values are determined, it is clear that the complexes containing the methyl substituents on the 5 and 6 positions of the phenanthroline moiety were the most cytotoxic with almost 98% cell death at 5 µM. The solubility of the complexes did improve by using N,N-dialkyl-N’-acylthiourea as ancillary ligands, however aqueous solubility remains a major problem. Sulphobutyl-ether-β-cyclodextrin (captisol) and low-molecular-weight surfactant micelles as drug delivery systems were considered in attempt to improve the solubility. DOSY NMR Spectroscopy revealed that there was no inclusion complex formation between the complex and capstiol, although the chemical shift trend suggested that there is at least some interaction. The low-molecular-weight surfactant micelles were considered as an alternative, which showed some promise as a drug delivery system, since the aqueous solubility improved and a colloidal suspension was obtained. / LG2018

Thesis (MTech (Environmental Health))--Cape Peninsula University of Technology, 2016. / Environmental remediation of organic and inorganic contaminants such as hydrocarbons has been a research focus area of interest. Chemical surfactants have been extensively used for the remediation of contaminated sites for immobilisation of hydrocarbons from environmental matrices. The focus has been on the impact of chemical surfactants on the environment. These petroleum-based chemical surfactants have raised serious environmental concerns as: 1) they are toxic, 2) they deteriorate the environment owing to their non-biodegradability, 3) they are costly, and 4) most are not intended for environmental applications. As such, alternatives had to be found to mitigate concerns associated with the application of such synthetic surfactants in bioremediation. Biosurfactants produced by microorganisms are a potential alternative to these synthetic surfactants. They have minimal environmental impact, are biodegradable and can withstand extreme conditions. However, biosurfactants are associated with high production costs and low production yield. Currently, large-scale production of biosurfactants cannot be achieved. Most research focuses on improving production yield which will contribute to the reduction in production costs. A lichenysin lipopeptide biosurfactant producing Bacillus sp., which grew exclusively on Beta vulgaris agrowaste, was identified. The microorganism was found to be an effective emulsifier for high molecular weight hydrocarbons such as, lubricant oil and diesel. The aim of this study was to improve biosurfactant production yield from this Bacillus sp., including emulsification efficacy by optimising fermentation conditions by supplementing the broth with biocompatible nanoparticles synthesised using a green chemistry approach with B. vulgaris (B. vulgaris) extracts. This study also aimed at reducing production costs by using B. vulgaris agrowaste exclusively as the production medium, both for the biosurfactant and the nanoparticles.

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Polystyrenes with carboxyl end-groups (PS-COOH)and poly (tert-butyl acrylates) (PtBA) of different molar mass were synthesised by anionic polymerisation using n-butyllithium as the initiator. Gel permeation chromatography (GPC) was used to calculate the molecular weight and polydispersity of these polymers. The tacticity of these polymers was determined using Carbon 13 Nuclear Magnetic Resonance Spectroscopy (13C NMR). FT-IR was used to confirm the tacticity of the samples. Matrix-assisted laser desorption ionisation time-of-flight mass spectrometry (MALDI-TOF) was used to confirm the presence of the carboxyl end-groups. All of the films studied in this project were transferred to mica substrates using the Langmuir-Blodgett deposition method. Both single layer and multiple layer films were constructed using this technique. Atomic force microscopy (AFM) was used to observe the surface topology of these films. / Doctor of Philosophy (PhD) (Science)