Insects respond to crowding, or to sublethal doses of insecticides, in many different ways. The "syndrome" of responses to crowding is comparable with that induced by the insecticides (dieldrin and D D T ) and this thesis examines the possibility that the syndromes are common responses to stress. The test insect, Dysdercus fasciatus Sign. exhibits some reactions to crowding which result in 'phase' phenomena in other insects, much of the mutual attraction being mediated through the antennae, especially the first segments of these. The extent to which the responses of the insects depend upon interference with their feeding patterns is investigated by deliberate modification of the diet, including the use of boiled cotton seed deficient in accessory nutritional factors. Insects reared in crowds resembled those from populations fed on this diet. Stressed insects tended to flutter their wings more than did unstressed ones. In general, slight stress, whatever the cause, seemed beneficial to the insects, but more severe stress influenced them adversely. To some extent crowding could suppliment the action of sublethal doses of insecticides in these respects. Particular attention was paid to the reproduction rate, the longevity, the size and composition of the eggs, and the tendency to aggregate, all of which responses were changed by conditions of stress. The practice of considering these responses as stress syndromes is shown to be a fertile source of ideas and experiments in investigations of this nature.

The incorporation of fluorine in epoxy resins has been the focus of research for many years, aiming to reduce water absorption and to improve the degradation resistance in hot-moist environments. To this end resins have been synthesised from fluorinated monomers while crosslinking was induced by conventional hardeners. In the present work conventional diglycidyl ether of bisphenol A epoxy resins were modified by the addition of small amounts of perfluoropolyether oligomers containing functional groups at the chain ends. Compatibilisation of these oligomers in epoxy resins was achieved through end-capping and chain extension reactions. Such modifications of the fluoroligomers only affect marginally the viscosity of the resin mixture. Using hexahydrophthalic anhydride as the main hardener and through selective curing procedures the morphology of the crosslinked resins was controlled to. produce either transparent formulations, consisting essentially of an IPN monophase structure, or opaque systems containing precipitated spherical particles. Perfect adhesion is exhibited at the particle interface with the matrix, i.e. there was a complete absence of de bonding during fracture.

With the rise of liquid soaps, and consumers becoming more environmentally conscious, manufacturers have two duties of care; one being to ensure adequate bug inhibition and the other to ensure that an excessive burden is not placed on the environment by any benefit agent. Recently there have been concerns about the excessive use of certain benefit agents. It is key to deliver the right amount of Triclosan (TC) to the right place at the right time so that at least the Minimum Inhibitory Concentration is delivered but not to over deliver which causes waste. The antibacterial TC has been studied as a model active ingredient in surfactant systems and on its own to contribute to the understanding of the lifecycle of active ingredients when used in soap formulations. The effect of TC in sodium dodecyl sulphate (SDS) and sodium laurate (SL) systems has been investigated using a range of physical chemistry techniques including UV-Vis and NMR to determine the increased solubility of TC in surfactant micelles. The effect of TC on the size and shape of SDS micelles has been examined using small angle neutron scattering. The surface tension of TC/ surfactant mixtures was studied to find the effects of TC on the critical micelle concentration (CMC) of the surfactant solutions: TC decreases the CMC of SDS and the effect is pH dependant. The partitioning of the poorly water soluble TC is dependent on pH as well as the concentration of surfactant. It is important to understand the partitioning in these soap system to understand factors such as bioavailability and deposition. I have proposed a model for partitioning between free TC and TC in micelles, and between anionic and neutral forms based on an NMR study. The phenol form of TC partitions much more strongly into micelles than the phenolate: when there is 1% SDS, there is 700 times more phenol in the micelles than in the bulk, whereas the proportion of phenolate in bulk and micelles is nearly the same. The partitioning of TC into supported lipid bilayers as models for cell membranes has been investigated by Total Internal Reflection Raman spectroscopy. In these experiments, TC was inserted into the bilayer at high pH and rinsed with low pH buffer. In these conditions TC is very resistant to rinsing from the bilayer. When bilayers with mixtures of lipids close to those found in bacterial cells were treated with TC, the bilayers were removed from the surface. The work described in this thesis has contributed to the investigation of surfactant systems in combination with TC and can be applied to other active ingredients in similar formulations as part of product development. I have investigated the state of the active ingredient TC in surfactant formulations through dilution and to delivery to one of the sites of action using appropriate physical chemistry techniques for each stage of the investigation.

No description available.

No description available.

Biosurfactants are surface active chemicals expressed by a range of organisms that reduce liquid (aqueous) surface tensions () of aqueous and aqueous-hydrocarbon (oil) mixtures. They are widely used in biotechnology, including agriculture, cosmetics, food, pharmacology and bioremediation, and many new biosurfactants are identified through surveys of bacteria recovered from a variety of environments. In this work, environmental Pseudomonas spp. were screened for biosurfactant production and behaviours determined in order to investigate the limits of biosurfactant activity and potential structural diversity within a phylogenetically related group of bacteria. A total of 355 pseudomonads and Pseudomonas-like isolates were isolated from activated sludge wastewater and potentially petroleum-contaminated soils from road side drainage (SUDS) site. These were phenotypically characterized using a number of growth and behaviour assays, including air-liquid interface biofilm formation in static microcosms and in a column bead system, and shown to be a diverse collection of isolates with a minimal level of biological replication (i.e. little evidence of identical strains recovered more than once in or between samples). Of these, 57 isolates were found to express biosurfactants in vitro by drop-collapse assay and confirmed by quantitative tensiometry. The surface tension of cell-free culture supernatants produced by these isolates was between 24.5 – 49.1 mN m-1, with a minimum theoretical surface tension (Min) of 24.2 mN m-1. This is in agreement with earlier predictions, suggesting a fundamental limit to the ability of bacterial biosurfactants to reduce surface tensions in aqueous systems. This finding suggests that further effort to isolate stronger active surfactants are likely to be wasted, and poses the interesting question of what biological or physical factors limit the production of stronger biosurfactants by bacteria. Differences in biosurfactant behaviour determined by foaming, emulsion and oil-displacement assays were also observed amongst select isolates producing surface tensions of 25 – 27 mN m-1, suggesting structural diversity in the biosurfactants produced. These findings provide a system for selecting biosurfactants for further chemical-structural analyses and future testing for various biotechnology applications where low surface activity, but varied behaviour is required.

No description available.

Surfactants comprise one of the largest volume commodity chemicals in the world and have multifarious uses from pharmaceuticals, agrochemicals, food, fuel and lubricant additives, paints and inks as well as detergents and cleaning agents. The ability to control surfactants once they are in solution is of great importance not only for scientific reasons but also because of environmental and economic interest. To this end, surfactants sensitive to changes in pH, temperature, C02, light and redox have already been developed. This thesis investigates a new class of surfactants designed to be magnetically active, whereby the composition and physico-chemical properties of a system may be perturbed simply by the switching "on" and "off" of a magnetic switch and with no significant energy input. The thesis demonstrates that these new magneto-responsive surfactants behave like conventional surfactants but are now bifunctional allowing for new magnetic approaches where previously magnetic nanoparticles have been employed. For example, the magnetic properties makes it easier to round up and remove the surfactant from a system once it has been added. By developing the first nanoparticle-free magnetic emulsions the potential for further applications in environmental clean ups (e.g. oil spills), water treatment or drug delivery have been demonstrated. In addition to this, the combination of surfactant adsorption and intrinsic magnetism has allowed for the control and manipulation of biomolecules without the need for magnetic nanoparticles. This work explores both the fundamental properties of these novel surfactants and also takes significant steps to optimize the surfactants for potential applications.

A number of synthetic approaches to preparing a metal-binding surfactant, containing the α-dioxime moiety, are described. Both linear and convergent synthetic methods have been unsuccessful in the preparation of a target surfactant. While the preparation of such a target molecule was not realised, some simple long chain α-dioximes have however been prepared in the course of investigating various synthetic methods. Microemulsion phenomena of these simple α-dioximes in aqueous surfactant micelles have been investigated by ultrasonic techniques, with the kinetics associated with such a process being determined. The kinetics of such α-dioximes in a co-micellar environment with nickel ions has been investigated under various conditions e.g. pH, surfactant concentration, and are reported. In order to prepare chiral functionalised long-chain surfactants of known configuration via "directed resolution" of diasteromeric amides obtained from racemic lactones, the alkylation of lactone enolates has been investigated. Only the enolate of γ-butyrolactone has been satisfactorily alkylated with long-chain electrophiles. Numerous attempts to alkylate the enolate of ε-caprolactone have been uniformly unsuccessful. Through optimisation of conditions a viable synthesis to α-alkylated derivatives of γ-butyrolactone has been found. "Directed resolution" of diastereomeric amides, prepared from the racemic γ-butyrolactone derivatives, have resulted in the isolation of optically pure lactones. Investigation of potential protecting groups for the α-diketone moiety in a functional surfactant synthesis resulted in the preparation of a 9,10-dimethyl substituted 1,4,5,8-tetraoxadecalin in a model study. Analysis of the AA′ BB′ multiplet couplings provided unambiguous evidence that the structure of this bicyclic molecule has the cis-configuration. Activation parameters for the ring inversion process between enantiomeric forms were obtained by line shape analysis of the variable temperature ¹H- and ¹³C-n.m.r. spectra.

No description available.