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Be sure to look at Dynamic Surface Tension while you are on your quest for knowledge. http://www.sensadyne.com/ was at the cutting edge of the field 15-20 years ago when I got the chance to co-develop some process control technology. Victor Jandle was the founder/inventor. He is wealth on information: http://www.sensadyne.com/importance-of-surface-tension

http://www.sensadyne.com/surface-tension-tutorial

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A unique dynamic fingerprint of any formulation can be generated in terms of surface tension versus surface age, from zero time to several minutes, using a differential maximum bubble pressure technique. This allows formulators and users to characterize formulation performance under all possible conditions before it is used. When multiple surfactants are used, the unique surface tension fingerprint may not be a “classical” dynamic curve, as different surfactants may diffuse to the interface at different rates, resulting in a complex dynamic curve with several peaks and valleys. In some cases, the lowest surface tension formulation may not be the best one to use because it can cause other problems.

THE MOLECULAR DYNAMIC SURFACE TENSION FINGERPRINT

Each fluid or formulation has a unique molecular fingerprint that is the tangential intermolecular force that keeps the fluid or formulation together, expressed in Dynes/Centimeter (or milliNewtons/Meter). This parameter is the Fluid Surface Tension; the force that keeps the fluid together at any air/fluid interface. It is the intermolecular force of attraction between adjacent molecules, expressed in force per unit width. Water, at ambient temperature, has a high surface tension in the range of 72 Dynes/Cm. while alcohols are at a much lower range of 20 to 22 Dynes/Cm. Solvents, typically, are in the 20 to 30 Dynes/Cm. range. If a simple pure fluid, or very complex formulation, changes at the molecular level then the fluid surface tension will change. We just have to measure it to see how the fingerprint has changed.

Pure fluids and pure solvents have a single surface tension value called “static” or “equilibrium” surface tension. If the formulation contains surfactants, then it will have a “dynamic” surface tension. This dynamic surface tension varies as the surface age varies; essentially a dynamic “fingerprint” of surface tension versus surface age; surface age being the amount of time the process allows surfactant molecules in solution to migrate to any newly created air/fluid interface, where their purpose is to lower the surface tension.

Surfactants are used in more than 100 industries and technologies, including scientific research. If surfactants are used, for example, in flotation, then either to lower the surface tension of water, then this role is important, but if, for example, to solubilize substances and increase their solubility or micellar catalysis or to obtain nanoparticles, then it is not. It all depends on which of the many properties of surfactants is used in specific studies or technologies.