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January 2007 |
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| Properties of Water in Colloidal and Biological Systems | ||||
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Dr. Carel Jan van Oss, an Adjunct Professor
and Professor Emeritus at the University of Buffalo (NY), has long been
a leading expert in the study of colloid and surface properties. He is
the author of Interfacial Forces in Aqueous Media (now it it's
second edition), and coauthor of Colloid and Surface Properties of
Clays and Related Minerals, Molecular Immunology: A
Textbook, and editor of Immunochemistry. All of the above books I
should mention are currently available on Amazon.com -- although there
is a wait for most of them. He's written or co-written numerous other
books and over 300 papers during his expansive career. The second edition of Interfacial Forces in Aqueous Media (2006) focuses on the understanding of polar interfacial and non-covalent interactions on macromolecules, biopolymers, particles, solid homogenous surfaces, cells, and polar as well as apolar polymers. The second edition also contains four new chapters dealing with interfacial tension and the properties and structure of water. In particular, the kinetics and energetics of protein absorption on metal oxide are examined. During the 1980's van Oss and others demonstrated how the contribution due to acid-base interactions can be expressed in terms of the product of their electron donor and electron acceptor components using a series of three liquids: one polar and two apolar. Water with either glycerol or formamide work well for the apolar components. The polar component might be methylene iodide or bromonaphtalene. This method of measurement, referred to as the Acid-Base method, is available in both ramé-hart DROPimage Standard as well as DROPimage Advanced software. After a series of contact angle measurements are taken using the three liquids sets, the surface energy is then calculated by DROPimage using Monte Carlo simulation. I had the opportunity to hear Dr. van Oss lecture this past summer in Toronto at the Fifth International Symposium on Contact Angle, Wettability, and Adhesion. In his lecture he detailed his discoveries relative to the little-understood physico-chemical properties of water and how these properties are the basis for the understanding of the polar interactions occurring in water. He explained his particular interest in the "hyper-hydrophobicity" of the water-air interface, the cluster formation of water molecules while in the liquid state, and the unusually high invariability of the ratio of the electron-accepticity to the electron-donicity of water in the liquid state as a function of temperature. This ratio is associated with the cluster size and contrasts with the typically defined polar cohesive energy which does not vary much with changes in temperature. These properties help us better characterize water as well as understand surface properties of ice and the water-ice-gas interfaces.
In September 2006 we featured Dr. van Oss in our Who's Who in Surface Science edition of this newsletter. There we detailed some of his other accomplishments. For example, prior to arriving in the United States, van Oss was a decorated WWII hero having assisted hundreds of Jews from Nazi invaders by forging documents on their behalf.
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