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The development of electrochemical techniques as applied to self-assembled supramolecular systems (e. g. micelles) has advanced over the past decade. The main properties that have been elucidated by these techniques have been micellar selfdiffusion and size. Although there are reports that have paid attention to the qualitative influence of intermicellar interactions on the behaviour of the micellar system, quantitative assessments of interaction are very limited. In this thesis, the application of rotating disk voltammetry, primarily, has led to a quantitative rationalisation of intermicellar interactions in cationic and nonionic micellar systems over a range of surfactant and electrolyte concentrations. Two `normal' micellar systems are studied with aggregates formed from cationic (CTAC) and nonionic (Triton X-100) surfactants. Initial measurements and analysis yields micellar sizes that are consistent with published values, demonstrating the validity and the ease of application of electrochemical techniques. Measuring self-diffusion coefficients over a range of electrolytes provides a comprehensive assessment of micellar phase behaviour and yields further structural parameters which are conventionally determined using a variety of methods. The first reported study of electrochemistry in a reverse micelle `nanoemulsion' is presented. The growth in micellar size on the addition of a solubilised probe gives important inferences for the careful control of particle growth in a reverse micelle `nano-reactor'. In summary, the thesis, as the title states, gives new insights pertaining to micellar structural evolution and interaction. The thesis will examine the benefits of applying electrochemical techniques to study micellar systems and concentrate, predominately, on the wealth of information that can be obtained by the resultant analysis. The work forms an excellent basis for not only further quantitative analysis but also as a phenomenological template for employment in the study of a diversity of self-assembled supramolecular species.

Gemini surfactants are an intriguing class of surface active agents that are comprised of two surfactant monomers chemically linked at or near the headgroups by a rigid or flexible spacer. In comparison to their corresponding monomer counterparts, gemini surfactants are more efficient at reducing surface tension, have better wetting properties, and typically have critical micelle concentration values that are one to two orders of magnitude lower. These intriguing properties characteristic of gemini surfactants make them of special interest for pharmaceutical applications. Within this work, two different projects were carried out to assess the pharmaceutical applications of gemini surfactants. The aim of the first project was to assess the applications of gemini surfactants as transfection agents for non-viral gene delivery by evaluating the physical stability characteristics of gemini surfactant-based lipoplex systems. Prior to this investigation, an evaluation of the interaction properties between gemini surfactants and DNA, and between gemini surfactants and the neutral helper lipid 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine was carried out using a combination of isothermal titration calorimetry, particle size, zeta potential and surface tension measurements. Following these evaluations, the physical stability of the gemini surfactant-based DNA delivery systems was assessed by examining the particle size distribution and membrane integrity characteristics of the lipoplexes. The results from this analysis revealed that the physical stability of these systems is limited by the membrane integrity characteristics of the lipoplex structure. The second project carried out was an evaluation of the interactions between gemini surfactants and a series of Tween surfactants commonly found in pharmaceutical formulations. The results from this analysis were analyzed using Clint’s, Rubingh’s, Motomura’s and Maeda’s theories for mixed micelle formation, where it was observed that there is a general synergistic mixing interaction present between gemini and Tween surfactants. The strength of synergism was found to be dependent upon the chain length and saturation of the Tween alkyl tail.

Th. doct.--Biol. cellulaire et microbiol.--Aix-Marseille 1, 1993. / 1993 d'après la déclaration de dépôt légal. Bibliogr. p. 143-151.

Th. 3e cycle--Pharm.--Paris 5, 1985. N°: 81.

Th. doct.-ing.--Génie chimique--Toulouse--I.N.P., 1983. N°: 288.

Orientador: Edivaldo Domingues Velini / Resumo: O presente trabalho teve por objetivo avaliar a tensão superficial de soluções com diferentes surfatantes. Utilizaram 180 tratamentos combinados de forma fatorial (15x12), correspondendo a quinze surfatantes (Ag-Bem, Agral, Aterbane BR, Agrex, Break Thru, Extravon, Energic, Fixade, Gotafix, Haiten, Herbitensil, Iharaguem, Lanzar, Silwet L-77 e Wil Fix) e 12 concentrações (0; 0,001; 0,0025; 0,005; 0,01; 0,025; 0,05; 0,1; 0,25; 0,5%; 1 e 2%). A análise estatística dos dados foi realizada com auxilio do programa SAS e para análise de regressão, adotou-se o modelo de Mitscherlich com algumas modificações (Y = 72,6 - A .(1 - 10 - C . X )), onde "A" e "C" são constantes, "X" é a concentração e "Y" é a tensão superficial. A expressão "72,6 - A" corresponde a mínima tensão superficial que pode ser alcançada com o surfatante em questão. A tensão mínima alcançada com os surfatantes permite dispo-los na seguinte ordem crescente: Silwet (19,08 mN/m), Break Thru (19,87 mN/m), Wil Fix (24,71 mN/m), Haiten (27,94 mN/m), Fixade (28,23 mN/m), Agrex (29,29 mN/m), Iharaguem (29,55mN/m), Herbitensil (29,66 mN/m), Agral (30,46 mN/m), Extravon (30,47 mN/m), Energic (30,74 mN/m), Gotafix (30,91 mN/m), Lanzar (32,41mN/m), Aterbane (32,68 mN/m) e Ag-Bem (32,71mN/m). Pelo coeficiente de eficácia (constante "C" do modelo de Mitscherlich) na redução da tensão superficial, os surfatantes foram dispostos na seguinte ordem decrescente: Break Thru (169,81), Silwet (143,43), Fixade (89,28), Herbitensil (63,74), Aterbane (46,38), Iharaguem (36,11), Extravon (30,39), Energic (27,81), Agral (24,31), Gotafix (22,68), Haiten (21,28), Ag-Bem (11,24), Lanzar (8,61), Agrex (4,01) e Wil Fix (1,52). Desenvolveu-se um procedimento alternativo para se calcular o coeficiente de micelização, a partir das curvas de tensão superficial em função das concentrações dos surfatantes. / Abstract: The objective of this research was to evaluate the static surface tension of solutions of the major surfactants used, in Brazil, as adjuvant in pesticide applications. It were considered 180 treatments arranged in a factorial scheme 15 x 12 with 15 surfactants (Break Thru, Silwet L 77, Fixade, Herbitensil, Aterbane, Iharaguem, Extravon, Energic, Agral, Gotafix, Haiten, Ag- Bem, Lanzar, Agrex e Wil Fix) and 12 concentrations v/v (0; 0,001; 0,0025; 0,005; 0,01; 0,025; 0,05; 0,1; 0,25; 0,5%; 1 e 2%). It were performed regression analysis and established models relating surfactant concentration to the surface tensions. The model best fitted to the data was Y = 72,6 - A.(1 - 10 - C . X )), corresponding to a modification of Mitscherlich model, where Y is the surface tension, X is the concentration of the surfactant, A and C are constants of the model. The expression "72,6 - A" is the minimum surface tension that could be achieved by the use of a certain surfactant and "C" was named efficacy coefficient and refers to the potential of each product in reducing the surface tension. The organosilicon surfactants were the most effective in reducing surface tension. The minimum tensions that could be achieved were 19,08 mN/m and 19,87 mN/m respectively for Silwet L 77 and Break-thru. The efficacy coefficients for both products were 143,43 and 169,81, also in a respective way. The other 13 non-organosilicon surfactants could be ranked in the following increasing order of minimum surface tensions: Wil Fix (24,71 mN/m), Haiten (27,94 mN/m), Fixade (28,23 mN/m), Agrex (29,29 mN/m), Iharaguem (29,55mN/m), Herbitensil (29,66 mN/m), Agral (30,46 mN/m), Extravon (30,47 mN/m), Energic (30,74 mN/m), Gotafix (30,91 mN/m), Lanzar (32,41mN/m), Aterbane (32,68 mN/m) and Ag-Bem (32,71mN/m). Considering the efficacy coefficients, the surfactants could be disposed in the following decreasing order... (Complete abstract, click electronic address below). / Doutor

The purpose of this research was to design and develop a facile synthesis of a series of multi-headed, two-tailed anionic surfactants (3CAm1(n)2) as anti-HIV microbicides, and to compare the biological activities of these compounds to the activities of their straight-acyl chain derivatives. The synthesis requires coupling reaction of dialkylacetic acid (R2CHCOOH) (R2= n-C6H13, n-C7H15, n-C8H17, n-C9H19, n-C10H21) and Behera's amine (H2NC(CH2CH2COOtBu)3). Commercially available diethyl malonate and straight chain alkyl bromide were selected to produce dialkylacetic acid. Sodium methoxide (MeONa) was used as a base to deprotonate the acidic protons of diethyl malonate. The monoalkylmalonate (RCH(COOEt)2) was separated by vacuum distillation and then used as the starting material of the dialkylation step. This modification improved the yields of this reaction by about 10 percent from the routine procedure of introducing both alkyl groups in the same reaction. The Behera's amine was prepared from the nitrotriester (O2NC(CH2CH2COOtBu)3) by Zn° reduction. The Behera's amine was then converted into an HCl salt by using a diluted HCl solution in 1:1 EtOH/H2O. By doing so, lactam impurity can be separated by solid-liquid extraction in hexane with sonication. The Behera's amine HCl salt was then separated and converted back into Behera's amine by Et3N in dry CH2Cl2. Dialkylacetic acid was converted into its sodium salt by using aqueous NaOH solution; the sodium salt was then added to SOCl2 to yield the acyl chloride (R2CHCOCl). The coupling reaction of Behera's amine and acyl chloride was done in dry CH2Cl2 with 2.2 eq Et3N under sonication to give crude (R2CHCONHC(CH2CH2COOtBu)3), which was identified by ¹H NMR. The crude product from coupling reaction was treated with formic acid. The resulting product was the purified and isolated as a white solid by gravity column chromatography in 100:100:0.5 Hexane/EtOAc/AcOH. Five homologues (R2CHCONHC(CH2CH2COOH)3 R2= n-C6H13, n-C7H15, n-C8H17, n-C9H19, n-C10H21) were produced by this method; all were fully characterized by ¹H and ¹³C NMR, IR, and HRMS. Future improvements can be achieved by replacing the carboxylate groups with the other anionic groups, such as sulfate and phosphate, or add making tri-tailed surfactants, and by, exploring other possible way to improve the biological activities. / Master of Science

This thesis is concerned with aspects of the surface and colloid chemistry of various microemulsion systems stabilised by pure nonionic surfactants and alcohol as well as mixtures of nonionic and anionic surfactants. Phase equilibria and interfacial characteristics of the systems are studied with a view to their potential usefulness for enhanced oil recovery, in which salinity and temperature are important parameters. The equilibrium microemulsion phases are scanned at different temperatures and salinities and thus interfacial boundaries can be determined and optimum salinity scans can be performed accurately using a modified spectrophotometer. Several analytical techniques (e.g., high performance liquid chromatography, gas chromatography, ion-exchange chromatography, mass spectrometry, viscometry, electrical conductivity, photon correlation spectroscopy, UV-spectrophotometry, thermogravimetric analysis, transmission electron microscopy, surface and interfacial tension techniques) have been used to characterise and understand the microchemistry of the microemulsion systems. Ultra-low interfacial tensions (>0.1 µN/m) can be achieved in the microemulsion systems. Surfactant transfer between phases, and phase inversion of micro emulsions are shown to occur around the condition which produces minimum interfacial tension. Adsorption of the surfactants from aqueous and nonaqueous solutions has been investigated and the results show that the extent of adsorption can be reduced significantly in the presence of alcohols (co-solvent). The extent of adsorption increases with increasing temperature and salinity; however, it decreases with an increase in the hydrophilic head group of the surfactant. Adsorption of nonionic surfactants on quartz from the nonaqueous solution (decane) is much greater than from aqueous solution. In microemulsion applications, droplet combustion of w/o microemulsions is also studied for different surfaces (i.e. silica, oxidised Fecralloy and catalyst coated Fecralloy) in the temperature range of 313-573K. Formaldehyde and acetaldehyde are formed as intermediate combustion products. Thus the microemulsion combustion can lead to new oxygenate products. The w/o microemulsion route is used to synthesize colloidal silica of controlled particle size and morphology. The particle size can be varied by changing the molar ratio of water to TEOS using a water pH of 10.5.