Research is centered on the evolution and application of principles of surface and colloid chemistry toward the solution of problems encompassing those systems where the properties of the phase boundaries govern physicochemical behavior. Although surface and colloid chemistry has traditionally been the domain of chemists, it is clear that the solution of actual problems requires not only considerable knowledge of the chemistry of surfaces, but also of transport phenomena, kinetics, electrochemistry, thermodynamics, and statistical mechanics. Fundamental progress in surface and colloid chemistry will occur only as these disciplines are jointly brought to bear, for the breadth of the field precludes compartmentalization. Furthermore, the complex nature of practical problems requires that experimental observations be employed to formulate theoretical models, and not vice-versa. This research program abstracts critical technical problems from important societal needs (currently, for example, enhanced oil recovery, catalyst synthesis, surfactant-based separation processes, and tear film stability), and attacks them at a fundamental level.
This research group is distinguished from most others in the discipline by several important philosophies. First, we work in the general area of surface phenomena, drawing as needed to solve problems from the fields of mathematics, transport phenomena, kinetics, electrostatics, optics, etc. Students are encouraged to obtain a strong background in traditional graduate chemical engineering. Surface chemistry is learned by apprenticeship. Second, we tackle research problems at a fundamental level. Sometimes the appropriate level is molecular and microscopic such as in our studies of ion, surfactant, organic acid, and polyelectrolyte adsorption at solid-liquid and liquid-liquid interfaces, flow and diffusion in narrow pores, kinetic interfacial resistances and dynamic tensions, dissolution kinetics of oxide minerals, synthesis of zeolites, electrostatics of colloid stabilization, conjoining/disjoining forces in thin films, and Monte Carlo simulation and Brownian dynamics of colloid suspensions. At other times, the appropriate level is more macroscopic, such as in particle capture kinetics and emulsion and bubble flow in porous media, in ion-exchange chromatography, in metal impregnation of catalysts, in ion diffusion in clay gels, in hydrodynamic stability of thin liquid films, in ultrafiltration of micellar solutions, and in modeling chemical oil recovery processes. Edisonian studies do not belong at universities, although they are difficult to avoid in the current funding climate.
Third, our work involves a strong experimental flavor. Thesis projects are not usually offered unless they involve both computational and experimental elements. Fourth, and most importantly, we believe strongly in obtaining quantitative explanations. Unfortunately, the history of surface chemistry is mainly one of reporting experimental results, followed by a qualitative discussion. Truth is much better established when phenomena are examined and tested under the strong light of a quantitative analysis.
The modeling and numerical analysis skills of the research group continue to blossom. This is evident in our catalyst impregnation kinetic modeling, the statistical-mechanical integral theories of structure in thin films, and the implementation of Monte Carlo and Brownian dynamics simulations. Likewise, we are now implementing more advanced and varied experimental techniques to probe molecular behavior. For example, in our current studies of metal activation of catalysts, we are employing X-ray diffraction, Raman spectroscopy, temperature-programmed reduction, and high-resolution transmission electron microscopy. NMR is also providing an exciting avenue for elucidating molecular structure, as in our studies of 27Al and 29Si in zeolite synthesis and of 129Xe in metal chemistry alteration during catalyst activation. We are making good progress using our traveling microwave and gamma-ray attenuators to detect local fluid saturations in porous media. Also, as part of our porous-media studies, we have learned how to prepare etched-glass micromodels replicating sandstone pore structures, so that we can observe pore-level events at micron scales. Finally, we have constructed a micro thin-film and topological interferometers for measuring thin-film shapes and thicknesses down to less than 25 Å. We are now gathering exciting information on film-drainage kinetics and on fundamental conjoining/disjoining forces. We anticipate constructing an ellipsometer to ascertain even smaller thicknesses. To our knowledge, we are the first to detect directly, oscillatory disjoining forces in thin liquid films and to explain quantitatively their origin as due micelle structuring. We are also the first to measure directly conjoining/ disjoining forces in pseudoemulsion films (i.e., gas/water/oil) and wetting films (i.e., oil/water/ silica) which proved to be difficult tasks.
These trends of increasing reliance of our research program on advanced theoretical and instrumental tools will continue. Two years ago Unocal donated a Brookhaven, argon-ion light scattering apparatus. We plan both static and dynamic light scattering on micellar solutions to garner sizes and interparticle potentials. We are now embarking on detection of organic solubilization inside micelles using changes in NMR T1 times. Our thin-film work is now expanding into grand canonical Monte Carlo simulations and X-ray reflection.
Our research program is maturing. It has a good, steady throughput of students and publications. Morale in the laboratory is high. Our work is well-recognized nationally and is well-known internationally. We are probably the leading academic laboratory in studying flow of dispersed fluids in porous media. Particularly, our work on foam flow in porous media is internationally acclaimed with numerous invited addresses abroad and two lengthy invited review papers. Our recent results on disjoining forces in thin films is garnering considerable international attention, with an invited review paper for Colloids and Surfaces and numerous invited lectures abroad. Also, the first national competitive fellowship in colloid science by the Henkel Corporation (1992), awarded to Maria Laso for her theoretical work on oscillary disjoining pressures in micellar films. Likewise, John Markels recently received a National Graduate Fellow Award from the North American Membrane Society (1993) for his thesis on micellar ultrafiltration.