The purpose of the work described in this thesis was the synthesis of a new class of surfactants containing chiral cationic end groups and the synthesis of two chiral reactant molecules which would react in the presence of these surfactants. The structures of the surfactant and substrate molecules were designed to maximize their stereochemical interactions and in this way reveal details of the nature of micellar catalysis. In order to indicate why these structures were selected, several examples of micellar catalysis and the factors influencing it will be discussed in the following pages.

The mobility of N-alkyl nicotinamides and their solubilization equilibria in surfactant micellar solution were investigated using an NMR paramagnetic relaxation method. The spin-lattice relaxation times (Tl) . for protons of these compounds were measured in pure D20 and in cationic surfactant solution in the presence and absence of · a low concentration of paramagnetic Ma2+ ions. The rotational motion of these molecules in aqueous phase became slower when the alkyl group changed from methyl to octyl. The increase of the 1H spinlattice relaxation rate (Rl) of the molecules, when surfactants are added, implies the penetration of these solubilizates into micellar phase. The micelle to water phase distribution coefficient, 1-p, was determined by monitoring the change of Rl of the solubilizates upon addition of paramagnetic ions to the aqueous phase. The mole fraction based distribution coefficient, Kx, as well as the free energy of transfer of N-alkyl nicotinamides from the aqueous phase to the micellar phase were calculated. A model was postulated for the interaction of N -alkyl nicotinamide with micelles. Hydrophobic force between the alkyl chains of the solubilizates and the surfactants accounts for the solubilization of N -alkyl nicotinamides and can force the binding of cationic compounds to cationic micelles · despite charge repulsion. With increasing of the alkyl chain length, the hydrophobic force increases, and the interaction between them becomes stronger, and more N -alkyl nicotinamides are solubilizated into the micellar phase.

This work was performed in the framework of an interdisciplinary graduate program that focuses on the establishment and extension of innovative compounds for the packaging of electronic systems. Such chemically or biotechnologically tailored compounds can be used for the direct patterning of optically, magnetically or biologically functional structures in nano- and biotechnical products. In order to organize matter at the nanometer scale, imprinting litho-graphy techniques or self-organization processes are appropriate. Fine-tuning of numerous engineering processes requires continuous and high precision monitoring as well as control of diverse parameters. These demands are only partially met by physical or chemical components since they use surrogate parameters, measure off-line, or provide insufficient performances. Biological compounds, in particular protein-based feedback systems, fulfill certain system requirements to a considerable degree. Hydrophobins and S-layer proteins are surface active proteins, produced by filamentous fungi or bacteria. In nature, these (self )assembly proteins form highly ordered and robust structures. In addition, their tolerance for different sequence manipulations and chemical modifications allows extensive functionalization of these nanometer-sized proteins. Hence, these surface active proteins can also be fused with other protein domains to create chimera, which retain function of both original proteins. In conclusion, both hydrophobins and S-layer proteins represent a versatile tool in numerous fields of applied biotechnology, medicine or diagnostics. But until now, efficient in vitro operation in molecular designed protein coatings is strongly restricted due to their complex assembly mechanism. In the first phase of this work, it was demonstrated, that representatives of class I and class II hydrophobins tend to form multilayered structures on solid surfaces. It was found that only two protein orientations seems to be preferentially formed. In the process of assembly, the orientation of the first hydrophobin layer strictly depends on the substrate wettability. Consequently, each of the following hydrophobin layers is inverse oriented to the layer before. This alternating assembly mechanism has to be taken into account, when working with functionalized hydrophobins, because a hydrophobin-fused functional protein domain is exclusively located on one side of the protein. Due to the densely packed structure of surface active proteins, a fused functional domain, embedded between two hydrophobins is barely available for external reagents. Basically, the simultaneous existence of a broad spectrum of ordered and disordered assembly structures, demonstrated the need of an uniform protein film assembly for applications in fine-diagnostics or biomedicine. With regard to molecular designed protein coatings, this work further aimed at establishing conditions to develop a method for a ‘layer-by-layer’ assembly of protein chimeras. Based on their amphiphilic character, self-assembly behavior of surface active proteins can be influenced by conventional ionic surfactants. In order to study the effect of surfactants on the composition and morphology of adsorbed protein films, contact angle measurements, nulling ellipsometry, SEM, AFM and AFAM were performed. It was found that the layer thickness of assembled protein films is strictly dependent on the amount of added surfactant. At certain threshold surfactant concentrations, hydrophobins and S-layer proteins assemble in uniform layers, which are as thick as expected for a protein monolayer or a bilayer. Assembled protein films are covered by a smooth surfactant layer, which prevents further protein assembly. AFAM measurements reveal the formation of well defined lattice structures under the coverage of surfactants. Even the removal of the surfactant layer is possible without inter-fering with protein specific secondary structures. Solvent accessibility and functionality of protein-fused domains was successfully demonstrated. As compared to conventional assembly techniques, this novel protein deposition method offers a possibility for a ‘directed’ protein coating on solid surfaces. In addition, it guarantees broadly ranged homogeneous assembly of protein chimeras on non-planar or even porous surfaces independent of their position. Finally, a prototype for an interfacial FRET was developed in a close collaboration with the Institute of Physical Chemistry (TUD). This innovative FRET between semiconducting nano-particles and illuminating protein chimeras takes place across an oil/water interface. Hydro-phobins were used to stabilize artificial oil droplets in aqueous solution. These small proteins possess the ability to attach fused functional domains very close to an oil/water interface. When, in addition to this, an optically active nanostructure directly docks to the hydrophobin, the distance of a protein-fused domain and the nanostructure are in the range of the FÖRSTER radius. It was successfully demonstrated that quantum dots and fluorescent proteins fulfill the spectroscopic requirements of such a donor/acceptor pair. The FRET performance of these excitable oil droplets was examined as a ‘proof of concept’. Due to its modular design, this signal amplification setup could be exploited in numerous fields of technical application ranging from quantification of micronutrient to photothermal cancer therapy.

Complexity in Home and Personal Care appears in several forms – the product, the substrate, and their interactions. The aim of this thesis is to investigate strategies for selecting effective surface-active agents (surfactants) that can be used in combination with other active ingredients in industry-relevant formulations deployed in the personal care sector. This thesis is composed of three parts, each of which involves a study of a complex natural system as it is affected by the addition of a complex chemical mixture. This is done in an effort to expose key features of the design rules for engineering the chemical mixture to enhance baseline performance via synergistic interactions of the formulation components and the natural system components. The first topic is an investigation on how the effectiveness of surface-active agents for removing a mixture of hydrophobic and hydrophilic soils from fabrics is related to the surfactants' physical-chemical features. The second topic is an exploration of compatible surfactant-enzyme systems that can be used in various industrial applications, where the behavior at a variety of interfaces is concomitantly important. Here, the focus is on the effect of surfactant structure and properties on enzyme function (i.e., activity), structural mobility and stability. The third topic is an investigation on the usefulness of micro-Raman spectroscopy for determining in situ chemical information that relates to the effects of a variety of surfactants on the mechanical and textural features of skin.

Effects of aqueous surfactant solutions upon cis/trans isomerization reactions of various N-alkyl-merocyanine dyes (II) were studied. Dramatic rate enhancements were found for all dyes in CTAB and SDS solutions above the CMC. CTAB solutions showed the greatest effect with some dye isomerizations catalyzed in excess of 1000-fold. Increases in either CTAB concentration or dye isomerization rates. N-methyl through N-pentyl dye isomerization rates were measured as a function of CTAB concentration and the data treated according to the pseudophase model for micellar catalysis. KS values ranged from 198 to 2000 M-1 for N-methyl to N-pentyl dyes, respectively. Micellar rate constants also increased as dye hydrophobicity was increased. Thermodynamic activation parameters were determined for N-methyl through N-hexylmerocyanine dyes in CTAB solutions. Rate enhancements in CTAB (above the CMC) relative to those in purely aqueous solutions were shown to be due to a substantial lowering of ΔH‡, for the various dyes. Increased CTAB concentrations of N-methyl dye solutions gave reaction rate increases resulting from a lowering of ΔS‡. In 0.054 M CTAB, increases in reaction rates with increased N-alkyl chain length were due to large increases ΔS‡ (from ca. 0 eu for N-methyl to 13 eu for N-hexyl). The data were discussed in terms of molecular interactions which can occur within the micellar solubilization sites.

No description available.

Even though edible oils undergo refining processes to remove undesirable components, commercial oils still contain small amounts of minor components that can contribute to either prooxidant and antioxidant pathways which ultimately affect the quality of the oils. The objective of this research was to determine the role of free fatty acids and mono- and diacylglycerols on the oxidative stability of oil-in-water emulsions. Free fatty acids acted as a strong prooxidants in stripped soybean oil-in-water emulsions. Concentrations as low as 0.1% of the lipid accelerated lipid oxidation rate by both shortening the lag phase of lipid hydroperoxide and hexanal formation. The results showed that the most likely mechanisms for the prooxidant activity of free fatty acids is through their ability to increase the negatively charge on emulsion droplets that in turn could attract the cationic transition metals to the emulsion droplet surface where they can interact with lipid and thus promote oxidation. The prooxidant activity of free fatty acids was dependent on fatty acid type with lipid oxidation rates being in the order of linolenic < linoleic < oleic. Surprisingly, an increase in the degree of unsaturation of the free fatty viii acids lowered the ability of the free fatty acids to promote oxidation which may be due to their differences in geometric shape thus influencing their ability to access the emulsion droplet interface and increase the negative charge. Overall, free fatty acids are strong prooxidants in oil-in-water emulsions. This prooxidant activity is dependent not only on their concentration but also on the molecular structure of the fatty acid. Addition of mono- and diacylglycerols in oil-in-water emulsions showed an antioxidative effect in both non-stripped and stripped soybean oil. Addition of 1-monooleoylglycerol only had a small impact on the oxidative stability of non-stripped soybean oil-in-water emulsions but did inhibit lipid oxidation in emulsions prepared with stripped soybean. Much stronger antioxidant activity was observed upon the addition of 1,2-dioleoyl-sn-glycerol to both non-stripped and stripped soybean oil-in-water emulsions. Both lipid hydroperoxide and hexanal formation decreased with increasing 1,2-dioleoyl-sn-glycerol concentrations with 2.5% 1,2-dioleoyl-sn-glycerol almost completely preventing hydroperoxide and hexanal production over the course of the study. Overall, these results suggest that diacylglycerols could be an effective antioxidant in oil-in-water emulsions which possibility due to their ability to form a liquid crystal phase which could form a physical barrier that decreases interactions between unsaturated fatty acids in the emulsion droplet core and prooxidants or oxygen in the aqueous phase of the emulsion. However, the antioxidant mechanism of diacylglycerols is not currently understood and needs further investigation.

In order to study the role of electrical charge existing on air bubbles in the kinetics of the particle-bubble adhesion process in froth flotation, the zeta potential of microbubbles in the 40 -to 80-micron size range have been determined by means of a simple microelectrophoresis technique. In general, the bubble charge is determined by the charge of the polar head of the surfactants when ionic surfactants are used to produce bubbles. However, the magnitude of the zeta-potential is reduced when the surfactants are hydrolyzed. When using nonionic surfactants, the bubbles exhibit isoelectric points (i.e.p) in acidic and neutral pH ranges. It appears that the location of an i.e.p. is determined by the acid-base property of the surfactant molecule used. The negative charges observed with air bubbles and oil droplets in the absence of surfactants can be explained by the differences in the hydration energies of H⁺ and OH⁻ ions. An increase in the concentration of ionic surfactants results in an increase in bubble charge. However, the increase is minimal or non-existant when nonionic surfactants are used. The flotation chemistry of the quartz-amine system has been studied using an induction time apparatus constructed in the present work which has a sensitivity limit of 100-150 micro-seconds. The basic unit is similar to the one used by Eigeles and Volova (1960) and Trahar (1983), but it operates with a micro-computer and has a greater sensitivity. It has been found that at a given dodecyl ammonium hydrochloride concentration, the induction time is at a minimum at approximately pH 10.5. At this pH, the collector hydrolizes to form neutral amine and the flotation recovery reaches a maximum, suggesting that iono-molecular species are the surface-active species responsible for flotation. This finding confirms the earlier conclusions obtained using the surface tension (Somasundaran, 1976; Finch and Smith, 1973) and the contact angle (Smith, 1963) techniques. The induction time measurements have also been conducted as a function of particle size, collector concentration, indifferent electrolyte concentration and temperature. The results are compared with flotation data, bubble charge, particle charge and film thickness. Results of the induction time and microflctation experiments conducted using bubbles and particles of known electrical properties indicate that if the potential on the air/water interface is increase to a high value with the same sign as that of the s/l interface (e.g. by adding a suitable surfactant) the flotation kinetic is retarded; conversely, surfactant of the opposite sign can enhance the adhesion process. / M.S.

The objective of this investigation was to observe and evaluate the effects of surfactants on the biodegradation of toluene in the subsurface. Soil microcosms containing gasoline were used to simulate conditions of an aquifer contaminated with hydrocarbons. The surfactants were the nonionics, Surfonic N-40 and N-95. Three volumes of gasoline, 0.005, 0.05, and 0.1 mL, were injected into separate microcosms in order to observe changes in toluene concentration in both adsorbed component conditions and free-phase, interstitial gasoline conditions. The data presented are the results from the microcosms containing 0.005 mL gasoline. -Dissolved toluene was only partially biodegraded in the microcosms containing free-phase hydrocarbons. The lack of complete biodegradation was believed to be due to substrate toxicity. / Master of Science

No / The influence of surfactants on the stability of cyclodextrin (CD) Pickering emulsions is not well understood. In this study, we report two-way effects of Tween 80 and soybean lecithin (PL) on the long term stability of Pickering emulsions stabilized by the self-assembled microcrystals of alpha-CD and medium chain triglycerides (MCT). The CD emulsions in the absence and presence of Tween 80 or PL at different concentrations were prepared and characterized by the droplet size, viscosity, contact angle, interfacial tension and residual emulsion values. After adding Tween 80 and PL, similar effects on the size distribution and contact angle were observed. However, changes of viscosity and interfacial tension were significantly different and two-way effects on the stability were found: (i) synergistic enhancement by Tween 80; (ii) inhibition at low and enhancement at high concentrations by PL. The stability enhancement of Tween 80 was due to the interfacial tension decrease caused by the interaction of Tween 80 with CD at the o/w interface at lower concentrations, and significant viscosity increase caused by the Tween 80-CD assembly in the continuous phase. For PL at low concentrations, the replacement of alpha-CD/MCT by alpha-CD/PL particles at the o/w interface was observed, leading to inhibitory effects. High concentrations of PL resulted in an extremely low interfacial tension and stable emulsion. In conclusion, the extensive inclusion of surfactants by CD leads to their unique effects on the stability of CD emulsions, for which the changes of viscosity and interfacial tension caused by host-guest interactions play important roles.