Advances in Colloid and Interface Science (v.103, #2)

An overview is given of sterol surfactants, including raw material aspects, classification and synthesis routes, physico-chemical behaviour and applications in pharmaceuticals and cosmetics.
Keywords: Sterol ethoxylates; Steryl glucosides; Environmental aspects; Physico chemical properties; Applications;

The most recent developments in the formation of new mesoporous templated zeolitic materials, characterized by surfaces of more than 1000 m2/g, are discussed in this paper. By adapting the synthesis parameters, such as type of silicium source, type of template, pH, temperature,… different materials can be synthesized with varying porosity and crystallinity. Besides the synthesis, much attention is focused on the activation of their surfaces by incorporation methods or deposition processes towards catalytic applications. Finally, the stability of the different materials, one of the critical parameters to potential industrial applications, is compared and evaluated.
Keywords: Mesoporous materials; Synthesis; Characterization; Catalysis;

Nature of contact angle hysteresis is discussed basing on the literature data (Colloids Surf. A 189 (2001) 265) of dynamic advancing and receding contact angles of n-alkanes and n-alcohols on a very smooth surface of 1,1,2,-trichloro-1,2,2,-trifluoroethane (FC-732) film deposited on a silicon plate. The authors considered the liquid absorption and/or retention (swelling) processes responsible for the observed hysteresis. In this paper hysteresis is considered to be due to the liquid film left behind the drop during retreating of its contact line. Using the contact angle hysteresis an approach is suggested for evaluation of the solid surface free energy. Molecular spacing and the film structure are discussed to explain the difference in n-alkanes and n-alcohols behaviour as well as to explain the difference between dispersion free energy γs d and total surface free energy γs tot of FC-732, as determined from the advancing contact angles and the hysteresis, respectively.
Keywords: Fluorocarbon; Contact angles; Hysteresis; n-Alkanes; n-Alcohols; Surface free energy;

The role of aqueous interfaces in the cell by Gerald H. Pollack (173-196).
The cell is rich with biopolymeric surfaces. Yet, the role of these surfaces and attendant surface–water interfaces has received little attention among biologists, most of whom consider water as a neutral carrier. This review aims to begin bridging the gap between biology and interface science—to show that a surface-oriented approach has power to bring fresh insights into an otherwise impenetrably complex maze. In this approach the cell is treated as a polymer gel. If the cell is a gel, then a logical approach to the understanding of cell function is through an understanding of gel function. Great strides have been made recently in understanding the principles of polymer-gel dynamics, and particularly the role of the polymer–water interface. It has become clear that a central mechanism in biology is the phase-transition—a major structural change prompted by a subtle change of environment. Phase-transitions are capable of doing work and such work could be responsible for much of the work of the cell. Here, we pursue this approach. We set up a polymer-gel-based foundation for cell behavior, and explore the extent to which this foundation explains how the cell achieves its everyday tasks.
Keywords: Polymer gel; Interfacial water; Phase-transition; Biological systems;