In this thesis, we examine the relationship between structure and dynamics in supercooled liquids from five unique perspectives. We first study a static length scale in the liquid and compare its growth on decreasing temperature with the growth of the logarithm of relaxation times, and find them to be almost strongly correlated. We find that this length scale can distinguish between several specially chosen model liquids whose structure at the level of two-body correlations are identical but whose dynamics at a given temperature are quite different. We then study the number of normal modes necessary to capture the rearrangements in a two-dimensional supercooled liquid as it moves between inherent structures. We find that the number of modes is quite small and decreases as the system is further cooled. After that, we study the effect of a frozen amorphous boundary on the dynamics of supercooled liquids and find that the range of the effect plateaus near that system's mode coupling temperature. We also identify a dynamical crossover at a higher temperature from these data by contrasting the relaxation behavior in the directions perpendicular and parallel to the boundary. After this work, we compare particle mobility with the position of particles deemed to be in preferred local packing arrangements. We find that the correlation between slow dynamics and the location of these locally preferred structures is highly dependent on the model investigated. Finally, we study supercooled liquids that have a fraction of particles randomly fixed in equilibrium positions. We find from annealing and rapid heating experiments on these samples behavior reminiscent of experimentally produced ultrastable glasses.

Polymer-Surfactant (P-S) systems and their implications both in industry and academia have been studied for the last fifty years. Despite the fact that the majority of synthetic and biological systems have a multicomponent nature, most previous studies focused on molecular interactions of individual polymers and surfactants in aqueous solutions, at the air/water interface or at the solid/water interface. P-S interactions in multicomponent systems have not received sufficient attention. Among the important issues that remain unresolved, the following are of particular significance: a) lack of information on P-S systems phase behavior in the presence of a third component which is widely used in industrial applications and of academic interest, b) insufficient quantitative information on competitive interactions of all species in the system and uncertainty on how molecules conform upon interaction and, c) lack of mathematical models to describe P-S interactions in a multicomponent environment. To address the unresolved issues, a study focusing on the mechanisms of interaction of an oppositely charged polyelectrolyte-surfactant (PE-S) pair in the presence of fatty acid (FA) was carried out. Experimental results using surface tensiometry, light scattering, zeta potential and, nuclear magnetic resonance (NMR) showed that the FA solubility in the system determined the overall phase behavior of the multicomponent mixture. In a system containing FA at a concentration above the solubilization limit of the surfactant, FAs form solid aggregates. Such aggregates were found to possess a considerable negative surface charge, consequently, preferential binding of the polycation to FA aggregates was observed and the usual tendency of PE-S pair to form a complex was inhibited. These results were useful to understand the polyelectrolyte-induced flocculation disruption by FA aggregates in emulsions systems. In a system containing FA at a concentration below the solubilization limit of the surfactant, the FA was found to be mostly solubilized forming mixed micelles with the surfactant. NMR revealed detailed information on the competitive binding behavior of both the fatty acid and the surfactant, including the morphology of aggregates at the polymer chain. Furthermore, solid state NMR showed how the structure and composition of the actual PE-S complex changed in the presence of FA. Finally, the law of mass action model is successfully employed to describe the PE-S surface tension profile in the presence of FAs.

Includes bibliographical references. / 1 v. : / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (D.Sc.)--University of Adelaide, Dept. of Chemistry, 1998

We report a performance comparison of two linear-scaling methods which avoid the diagonalization bottleneck of traditional electronic structure algorithms. The Chebyshev expansion method (CEWI) is implemented for carbon tight-binding calculations of large systems and its memory and timing requirements compared to those of our previously implemented conjugate gradient density matrix search (CG-DMS). Benchmark calculations are carried out on icosahedral fullerenes from C60 to C8640 and the linear scaling memory and CPU requirements of CEM demonstrated. We show that the CPU requisites of CEM and CG-DMS are similar for calculations with comparable accuracy.

Thesis (Ph. D.)--University of Texas at Austin, 1999. / Vita. Includes bibliographical references (leaves 109-111). Available also in a digital version from Dissertation Abstracts.

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In this thesis, attempts have been made to correlate some equilibrium properties of microemulsions with the formation and stability of macroemulsions. Studies have been mainly limited to water-in-oil (W/O) systems stabilised by pure nonionic surfactants of the poly-oxyethylene alkyl ether (CnEm) type. Initially however, a brief account is presented of the behaviour of W/O microemulsions stabilised by commercial nonionic surfactants of the type used in foods.A detailed study of the equilibrium behaviour of W/O microemulsions stabilised by tetra-oxyethylene mono-n-dodecyl ether, C12E4,in hydrocarbon oils is presented. Aggregates form above a certain surfactant concentration in the oil, designated the critical microemulsion concentration, cμc. Changes in the monolayer curvature induced through changing the temperature, salt concentration and the nature of the oil phase, are discussed in terms of an effective surfactant molecular geometry. The effect of solubilisation of protein into the dispersed aqueous phase is also presented.The corresponding W/O macroemulsions prepared with these systems at concentrations in excess of the cμc breakdown primarily by droplet sedimentation. There appears to be an optimum surfactant concentration at which maximum stabilisation is achieved. This is approximately equal to the cμc of the surfactant in the oil phase. Addition of microemulsion droplets to the oil dramatically increases the rate of oil phase resolution. For a fixed concentration of aggregated surfactant, the acceleration rate is rather insensitive to the size of the microemulsion droplets. These findings are reasonably consistent with a depletion flocculation mechanism in which microemulsions are assumed to behave as hard spheres and are excluded from the intervening region between approaching emulsion droplets.Microemulsion phase behaviour is also reported for oil phases containing different concentrations of medium and long chain length triglycerides (MCT, LCT) in heptane. The critical microemulsion concentration is observed to increase dramatically upon increasing the concentration of triglyceride. Additionally, the enthalpy change upon transfer of a mole of C12E4 monomers from the oil phase to the preferred microemulsion droplet curvature becomes significantly less exothermic as the concentration of MCT in the oil phase increases.The breakdown of W/O macroemulsions produced with these triglyceride systems is also consistent with a depletion flocculation mechanism. Emulsions prepared with 75% MCT as the oil phase undergo coalescence once an approximately closepacked droplet volume fraction is achieved. It is shown that as the cμc increases (through the addition of MCT or increasing the temperature), the stability of the emulsion dramatically decreases.Using a technique of time-resolved fluorimetry, the rate of exchange of probe molecules between microemulsion droplets has been determined. The exchange rate is always slowest at the solubilisation phase boundary where inter-droplet attractions are a minimum. The rate constants at this phase boundary are similar for aggregates formed in both heptane and in an equal volume ratio mixture of heptane : MCT. The possible relevance to the magnitude of the exchange rate constant of energies associated with bending the surfactant monolayer and desorbing surfactant from the droplet surface are considered.This technique has also been applied to three surfactant systems for which monolayer bending rigidities have previously been reported. Microemulsion exchange rates measured at equivalent positions on the solubilisation phase boundary increase as the monolayer rigidity decreases. The stability of the corresponding W/O macroemulsions is also observed to follow this order, the fastest water resolution rates being observed for the systems with the lowest monolayer rigidities.

The enantioselective hydrogenation of α-ketoesters over supported platinum metal catalysts which have been modified by chiral molecules has been studied. The aim of this thesis was (a) to gain a greater understanding of the kinetics of asymmetric hydrogenation of methyl pyruvate (MeCOCOOMe) to methyl lactate (MeCH(OH)COOMe) over cinchonidine modified EUROPT-1, (b) to diversify the reaction, by variation of the metal, modifier and reactant and (c) to test and develop a mechanism to explain the reaction by both mathematical and molecular modelling. It was found that only very small quantities of cinchonidine modifier were required to render EUROPT-1, a 6.3 % Pt/silica catalyst, suitable for asymmetric hydrogenation of methyl pyruvate. The plots of the variation of with reaction rate and of optical yield with modifier loadings reached plateau values at a loading of ca. 0.8 mg cinchonidine per 100 mg EUROPT-1. The shape of the curves has been fitted to a mathematical model which gives evidence that the mechanism is a result of a 1: 1 interaction between modifier and reactant. Modification of catalyst by mixtures of cinchonidine and cinchonine, or of quinine and quinidine has been performed and results obtained as to the effect on reaction rate and optical yield. The variation of the latter with the mole fraction of modifier has been fitted to a mathematical model which supports the view that the mechanism is a result of a 1: 1 interaction. It has been discovered that Iridium, especially when supported on calcium carbonate, is an effective catalyst for both racemic and enantioselective hydrogenation of methyl pyruvate. When Ir/CaCO³ was reduced and modified by cinchonidine, hydrogenation of methyl pyruvate at 273 K and 10 bar in ethanol resulted in an optical yield of 39 %. The reaction is approximately zero order in reactant and first order in hydrogen, being first order overall. The apparent activation energy was 22 ±2 kJ mol-1. The unmodified reaction proceeded at a very fast rate with an apparent activation energy of 11 ±2 kJ mol- 1. The enhanced rate was explained in terms of stabilisation of the halfhydrogenated state by the carbonate support. Rhodium, Osmium and Rhenium were found not to be effective for asymmetric hydrogenation, which in the case of rhodium is contrary to the literature. Diversification of the modifier was found to be possible, the best alternative being by the use of 10,1 1-dihydroquinine 4-methyl-2-quinoyl ether which gave an optical yield of 22 %. The amino acids tryptophan and histidine were found to give poor but reproducible enantiomeric excesses. Ephedrines and benzyl pyrrolidine methanol were found not to be effective modifiers which is contrary to the literature. A molecular modelling study resulted in a new proposal for the asymmetric hydrogenation site which explained the mechanism in terms of a 1:1 interaction between modifier and reactant at the catalyst surface. The proposal successfully accounts for the observed enantioselectivity in terms of steric hindrance to the unwanted product. The proposed mechanism is in agreement with experimental data in the literature.

Electroless plating is the controlled chemical reduction of metals without the use of an applied external potential. The use of electroless plating has a number of advantages over electroplating including the ability to deposit coatings onto complex-shaped objects which can be metallic or non-metallic, such as plastics. The most widely used electroless coating is electroless nickel prepared using sodium hypophosphite as reductant. This results in coatings which contain phosphorus. The properties of metal coatings containing non-metals are frequently superior compared to those of the pure metal.The first part of present work was concerned with the development of an electroless plating solution capable of depositing palladium-boron coatings. The plating solution is based on EDTA-stabilised palladium (H) ions in the presence of dimethylamine borane as the reducing agent. At a pH of 10.5 the solution deposits bright adherent coatings at 1 μm per 10 h. The plating solution operates at room temperature within narrow limits of composition and concentration: small deviations in composition from the optimum results in solution decomposition.Characterisation of electroless palladium-boron coatings indicates that the inclusion of boron decreases the corrosion resistance of the coating. Examination of palladium-boron coatings by X-ray diffractometry show that the lattice parameter has been increased by 2.86%.The second part of the present work was concerned with the development of pure ruthenium coatings. The plating solution developed uses hydrazine hydrate as the reducing agent with methylamine as stabiliser. The plating solution operates at a pH of 13 and at 60°C, and deposits 65% of the available ruthenium in 5 h. This corresponds to a 3 gm coating over a substrate surface area of 25 cm2.The coatings produced are bright and adherent. The roughness of the substrate surface was found to be important to obtaining adherent coatings over 2 gm thick. A roughness in the order of 1100 A was found to be satisfactory. Scanning electron microscopy shows the coatings to be dense with no obvious pores. The porosity of the coatings was found to be low, decreasing with increasing coating thickness. However, the electrochemical properties of the coatings indicate that ruthenium coatings have poor corrosion resistance.The chemistry of the plating solution, particularly for ruthenium, is considered in some detail.