Self-assembled monolayers (SAMs) offer a convenient approach for fabricating molecularly tailored interfaces with well-defined compositions, structures, and thicknesses. SAMs have been suggested for use as corrosion barriers, antifouling coatings, and as components of molecular electronics and lithography. Still, researchers lack the molecular description of the interfacial properties, structural features, and barrier properties of SAMs that would be useful for optimizing and tailoring the behavior of SAMs. This dissertation makes connections between the molecular level structural features of SAMs and macroscopic properties such as wettability and barrier properties using molecular dynamics (MD) simulations and experimental techniques. MD simulations were performed to explain the unexpected experimental observation that the wetting properties of some liquids on SAMs prepared using alkanethiols (CnSH) depend on whether the chain length (n) is odd or even. The difference in near-surface structure of the liquid (and not that of reorganization events by the monolayer) appears responsible for the high sensitivity of hexadecane and the general insensitivity of water to the structural differences expressed by odd- and even-chained monolayer surfaces. MD simulations were also performed to investigate the influences of molecular structure on the ability of n-alkanethiolate SAMs on gold and copper to act as barrier films against through-film oxygen transport as relevant to the uses of these films in corrosion inhibition. The barrier resistances offered by these films towards oxygen transport, as calculated by the MD simulations, were a function of the crystallinity of the center region of the SAMs. Upon the introduction of an ether linkage within the SAM, the results from MD simulations show that when the ether linkage is too close to the metal surface or to the chain ends, the free energy barrier of SAMs towards oxygen diffusion was almost 10 kJ/mole less than that for an n-alkanethiolate SAM having the same chain length. Phytanylthiol (3, 7, 11, 15-tetramethyl-hexadecanethiol) SAM on gold was characterized by ellipsometry, wetting measurements, X-ray photoelectron spectroscopy, and MD simulations to gain insights into the effect of a branched chain on the thickness, chain packing and orientation, wettability, and barrier properties of a SAM. These experimental and computational studies indicate that phytanylthiolate SAM on gold contains a fully extended 16-carbon backbone which is more disordered as compared to n-hexadecanethiolate monolayer on gold, with the sulfur head group possibly occupying four-fold hollow sites on gold.

Fluids are defined as complex due to their size, shape, polydispersity, or specific intermolecular and intramolecular interactions. Success in modeling complex fluids and their mixtures is contingent upon the ability of the molecular model to describe specific interactions, and capture the size and shape effects governing the phase behavior of the systems. Molecular models based on Wertheim's Thermodynamic Perturbation Theory of first order incorporate detailed information regarding the architecture of the molecules and their microscopic interactions, thus representing fluids and their mixtures with a high degree of realism. In particular, the Statistical Associating Fluid Theory (SAFT), as well as its later versions (e.g., Perturbed Chain-SAFT), have emerged as powerful tools for modeling complex fluid systems. The developments presented in this dissertation can be broken down into two components that separately focus on the bulk and interfacial aspects of the considered systems. The bulk part focuses on modeling phase behavior of polyethylene solutions. Based on experimental studies of the phase behavior of Linear Low Density Polyethylene, a simple and effective modeling concept for branched polyolefins is proposed in the framework of PC-SAFT. The model, extensively validated by comparisons to experimental data, is used to study the influence of a short-chain branching distribution on the phase behavior of polyolefins. The PC-SAFT equation of state was the underlying thermodynamic model used in the studies of branched polyolefins. A shortcoming of PC-SAFT identified during the work---systematically erroneous predictions of the phase behavior of polymer solutions at high polymer concentrations---motivated the development of a new equation of state for chain fluids. The SAFT-Dimer model describes the phase behavior of long chain fluids and polymers with high accuracy. On the interface side, a recently developed density functional theory (DFT), based on Wertheim's Thermodynamic Perturbation Theory of first order, is applied in conjunction with SAFT to predict the interfacial properties of hydrocarbons and polymers. The self-consistency of the bulk and interfacial models is of critical importance to several applications in which interfacial properties of the considered systems need to be predicted based on the readily available bulk properties.

The creep of polymethyl methacrylate was investigated in four-point flexural loading mode. Measurements were taken at temperatures from 8$\sp\circ$C to 55$\sp\circ$C, time periods up to 450 hours and stresses ranging from 5 to 25 MN/m$\sp2$. The data obtained were successfully superposed vertically; the data reduction, in this way, was expressed in the form of a constitutive equation: e(t, T, S) = e$\sb0$ (ref). exp $\lbrack-(\Delta$H$\sb0$ $-$ $\beta$S)/R. (1/T $-$ 1/T$\sb{\rm ref}$)).exp ($\beta$/RT. (S $-$ S$\sb{\rm ref}$)). t$\sp{\rm n}$ which shows that the creep strain (e) may be obtained as a product of separable functions that express the effect of time (t), temperature (T) and stress (S). Subscript ref. indicates the chosen reference state. The creep behavior follows a power law time dependence with an exponent equal to 0.24. The apparent activation energy of the creep is independent of temperature (Arrhenius behavior), stress dependent and decreases with increasing stress.

Experimental evidence suggests that contact angle hysteresis is related, in some cases, to surface roughness or heterogeneity on a microscopic scale. This work investigates the effect of periodic roughness or heterogeneity on quasi-static motion of a liquid/vapor/solid contact line. We determine the static stable equilibrium configuration(s) of the liquid/vapor interface in a system by minimizing the sum of the Helmholtz free energy and gravitational potential energy (or the total energy) of the system. This is the energy principle. Our model presumes that both the surface of the solid and the liquid/vapor interface can be generated by drawing normals through a curve in a vertical plane. The solid is dipped into a liquid reservoir. A uniform gravitational field is present. The Young's Law contact angle varies along the curve in the vertical generating plane corresponding to the surface of the solid. Only a single contact line is allowed. This model is a much more general treatment of these problems than found in the literature. Application of the energy principle results in a family of possible liquid/vapor interfacial configurations. The capillary length of the liquid/vapor pair is the determining length scale of the model. If the wavelength of surface roughness or heterogeneity is much smaller than the capillary length, then hysteresis of the apparent contact angle occurs. (The apparent contact angle is measured as though the surface of the solid is a vertical plane.) The effect of relaxing the single contact line assumption is studied when the solid boundary surface is a sawtooth. Here, the general framework of the model breaks down. However, this case is treatable using a more specific theory. In certain cases, trapped droplets or bubbles are formed which are stable in a limited technical sense, and which suppress apparent contact angle hysteresis. Then the apparent contact angle may approach either 180$\sp\circ$ or 0$\sp\circ$ as the wavelength of the boundary surface approaches zero.

A systematic analysis of the structure of char particles produced from an Illinois #6 coal was carried out. Coal particles were pyrolyzed in a hot-stage reactor under inert (N$\sb2$) and reactive (5% O$\sb2$ / 95% N$\sb2$) atmospheres at various heating rates (0.1, 1 and 10$\sp\circ$C/s) and final heat treatment temperatures (500 and 700$\sp\circ$C). Image analysis procedures were used to measure the size and macroporosity of the particles, and the surface area and size distribution of the macropores. High heating rates and the addition of oxygen resulted in larger particle swelling and increased the macroporosity, the surface area and the fraction of large macropores with thin walls. Heat treatment temperatures had smaller effects on char particle structure. Our data confirm the strong effects of pyrolysis conditions on char reactivity during combustion in the diffusion-limited regime. They also provide the necessary parameters for char combustion models.

Cure shrinkage is an inherent property of polymerizing systems due to the conversion of secondary bonds between monomer (or prepolymer) molecules to primary bonds, which have smaller interatomic distances. Cure shrinkage is highly undesirable: it impairs dimensional control and causes poor surface finish in molded polymers; it also generates setting stresses in highly filled systems. Previous methods for cure shrinkage control require special materials and conditions or entail the formation of voids. In this investigation, two processes were developed for producing polymer systems with zero shrinkage or slight expansion: (a) use of ammonia-modified montomorillonite as additive; and (b) microphase separation. The first method utilizes the dilatation of specially-modified montmorillonite (MMT) particles to counteract resin polymerization shrinkage. The MMT particles are first processed by replacing part of their hydration water with ammonia (which forms coordination bonds with SiO$\sb2$ in the mineral crystal) then dispersed into the resin. During cure at ambient temperatures the polymerization exotherm raises the temperature to 60-80$\sp\circ$C, breaking the SiO$\sb2$-NH$\sb3$ bonds; however the liberated gaseous ammonia cannot escape outside the resin-embedded MMT particles and forces them to dilate to more than twice their original size. By controlling the amount of ammonia-modified MMT added to the resin (in amounts of 6-10%) we obtain cured systems that show zero shrinkage and have no setting stresses. This can increase their strength by ca. 20-40%. The second method achieves cure shrinkage control by microphase separation. Certain multicomponent acrylic systems, when polymerized rapidly, separate into microdomains of different phases with a corresponding reduction in cure shrinkage. We attribute this phenomenon to lower efficiency in molecular chain packing at the interphase boundaries; the phase separation itself is attributed to local, diffusion-controlled composition changes during rapid cure. Accumulation of the local volume increase as the microphase boundaries gives rise to the observed reduction in cure shrinkage.

Various model systems containing pure compounds of oil, water, and surfactant were studied to understand equilibrium phase behavior and nonequilibrium phenomena, especially their relationship to solubilization-emulsification mechanisms of detergency. Videomicroscopy was used to observe nonequilibrium phenomena such as intermediate phase formation, interfacial instabilities, and spontaneous emulsification. Of particular interest was observation of time-dependent behavior using a newly developed dynamic contacting technique where a small drop of oily soil was injected into an aqueous surfactant solution. It is important to know whether formation of an intermediate phase occurs since it brings about a substantial improvement in detergency, provided that it is capable of solubilizing significant quantities of oil. Diffusion path theory was used to predict conditions for intermediate phase formation. Results of contacting experiments for anionic and nonionic surfactants with pure polar oils were in good agreement with theoretical predictions based on this theory. Systems containing the pure triglyceride triolein and nonionic surfactants were studied. For the C$\sb{12}$E$\sb5$ system, soil removal was higher than with C$\sb{12}$E$\sb5$ and C$\sb{12}$E$\sb4$ due to formation of an intermediate microemulsion (D) phase capable of solubilizing triolein. For mixtures of triolein and n-hexadecane the D phase was found at low triolein contents and the D$\sp\prime$(L$\sb3$) phase having low solubilization of both oils at high triolein contents. Phase and dynamic behavior of a system containing mixtures of a pure nonionic surfactant and an anionic surfactant of the alkyl ethoxy sulfate type were studied. Rapid solubilization of oil was observed with videomicroscopy near the Phase Inversion Temperature (PIT) due to the formation of an intermediate middle-phase microemulsion. Soil removal was greatest near the PIT. Finally, oil drop contacting experiments were performed for mixed hydrocarbon-long-chain alcohol soils with different pure nonionic surfactants. Delayed formation of an intermediate liquid crystalline phase was observed for conditions above the PIT where excellent soil removal was also found. A quasi-steady state analysis requiring relatively little information on phase behavior was able to explain observed effects of drop size and surfactant concentration on the time when liquid crystal formation began.

Infinite-dilution fugacity coefficients were obtained for the binary system fluorene/phenanthrene at thirteen temperatures by fitting total pressure across the entire mole fraction range by a computer routine. A thermodynamically consistent routine, that allowed for both positive and negative pressure derivations from the ideal values, was used to correlate data over the full mole fraction range from 0 to 1. The four-suffix Margules activity coefficient model without modification essentially served this purpose since total pressures and total pressure derivatives with respect to mole fraction were negligible compared to pressure measurement precision. The water/ethanol system studied by Kolbe and Gmehling and binary systems studied by Maher, Srivastava and Smith comprised of aniline, chlorobenzene, acetonitrile and other polar compounds were fit for total pressure across the entire mole fraction range for binary Vapor-Liquid-Equilibria (VLE) using the rigorous, thermodynamically consistent expression derived by Ibl and Dodge from the Gibbs-Duhen Relation. Data correlation was performed using a computer least squares procedure. Infinite-dilution fugacity coefficients were obtained using a modified Margules activity coefficient model which gives residual values of x$\sb1$ dly$\gamma\sb1$ + x$\sb2$ dln$\gamma\sb2$ across the mole fraction range that lie between the value of vd$\Pi$/dx$\sb1$/RT at x$\sb1$ = 0 and x$\sb1$ = 1. x$\sb1$ and $\gamma\sb1$ and x$\sb2$ and $\gamma\sb2$ are the mole fraction and activity coefficient of components 1 and 2 respectively. v is the mixture liquid molar volume, $\Pi$ is total pressure, R is the ideal gas constant, and T is temperature in absolute units. This correlational procedure, a modified Margules model, yielded infinite-dilution fugacity coefficients differing from the non-rigorous Margules model (derived for a binary at constant pressure) by a few percent but in some cases by as much as ten percent. The modified version is necessary in fitting binary total pressure versus mole fraction data to an expression totally consistent with Gibb's Phase Rule. Its application implies that the derivative of pressure with respect to mole fraction may affect the values of activity coefficients determined, especially at either infinite-dilution axis where the absolute value of this derivative is greatest.

Certain properties of the back-propagation neural network have been found to be potentially useful in structuring models for process control applications. The network's relative simplicity and its ability to learn by example are potentially important in the effort to develop automated continuous on-line system identification. The capacity of the network to form nonlinear mappings enhances research designed to advance nonlinear system identification techniques. Since most real processes are nonlinear, this prospect can have wide impact. The unstructured nature of the network model was found to be controllable by techniques developed in the study. Care must be taken to identify and train the network with consistent data that contains sufficient dynamical information. Model-based fine tuning of a controller using a network model that was identified with closed-loop data was successful for the linear and nonlinear systems examined. The utility of the model is a function of the dynamical history of the process. When the information content of the data is sufficient, the network can capture the most important features of system behavior so that fine tuning can be based on optimal parameters such as integral absolute error. This method offers a more complete picture of tuning options than that of other fine tuning techniques such as trial and error, which are not based on a system model. The techniques developed in the tuning effort may be extended to closed-loop model identification for the purpose of controller redesign. In this case, successful identification probably depends on the continuous on-line identification to correct for modeling error.

A new simplified fully implicit compositional simulator has been developed. This simulator is different from existing models because it combines the conventional black oil equations with a compositional injection component equation. Sets of two dimensional pvt and injection component K value tables at constant pressure and variable mole fraction injection component are generated using a cubic equation of state used in the compositional simulator. The data are generated from a series of cells loaded with the initial composition of the reservoir. Pore volume increments of injection gas are cycled through the cells in sequence, with oil and gas volumes passing downstream in proportions calculated by the relative permeability curves. This pvt test replicates a one dimensional compositional cycling process at fixed pressure. The resulting data describes a unique compositional path through the phase diagram for constant pressure and variable mole fraction injection gas, and this path is independent of cell position in the simulator. The simulator runs at speeds that far exceed the speeds in current compositional simulators, primarily because the speed is independent of the number of components. Small problems with several hundred cells typically run about 10 times faster, and larger speed increases are realized for bigger problems. The simulator has been tested successfully for gas cycling projects including the Third SPE Comparative Solution Project and CO2 flooding projects. Results for constant and variable pressure cycling, with and without vertical crossflow were in good agreement with a compositional model.