Interfacial Phenomena Near Critical Points

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w:\awards\awards96\*.doc 9631133 Law This experimental research project is concerned with surface phenomena of adsorption and wetting, which play an important role in many physical, chemical, and biological processes. The research is based on a recently developed ellipsometric microscope. This instrument, developed in the PI's laboratory, will be used to determine size and shape of droplets under experimental conditions. The data will be compared with appropriate theoretical models. This study will enhance our understanding of how uniform wetting layers form via droplet growth and coalescence, how ions in the solution influence the phenomena of wetting and adsorption, and will clarify whether or not orientational order is important at the surfaces of critical ionic mixtures. %%% The composition at the surface of a solution frequently differs from that in the bulk because surface interactions create an adsorbed layer or a wetting layer at the interface. These surface effects are important in many processes such as lubrication, catalysis, and fluid flow, through biological membranes and porous media. The work will use an ellipsometric microscope to study the dynamics of coalescence and growth as wetting droplets combine to form a uniform wetting film at the surface of a critical non-ionic binary liquid mixture. The dynamics will be studied as the temperature is varied. The influence of ions will also be studied. This work will enhance our understanding of the complex interplay between bulk critical phenomena and surface processes, in the presence and absence of ions in solution. ***