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Fundamental Research

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Fundamental Surfactant Research

Research sponsored by IASR encompasses a wide spectrum of technological applications as outlined in previous sections. However, members of the Institute strongly believe that the underlying forces responsible for the phenomena of surfactant behavior must be understood in order to provide a firm basis for applying knowledge to practical problems, Fundamental research is a basic part of the program at IASR, both in relation to specific technological problems and as a part of the larger goal of improving our understanding of surfactant behavior in general.


Institute for Applied Surfactant Research - Fundamental Surfactant Research

A characteristic property of surfactant molecules is their tendency to aggregate at interfaces. Examples are adsorption on solids and monolayer formation at an air-water interface. Surfactants will sometimes create their own interface by forming very small aggregates like micelles or vesicles to remove a portion of their structure from contact with a solvent. On the other hand, surfactant aggregates can form separate thermodynamic phases such as microemulsions and coacervates.

An important facet of research at IASR is the investigation of the similarities and differences between the many aggregates that surfactants can form, both in single surfactant systems and in mixtures of surfactants. Because some of the same effects are responsible for the formation of many of the aggregates, comparison of aggregation thermodynamics can shed light on surfactant interactions in the process of clustering under different conditions. This type of approach, which should lead to comprehensive theories of several aggregation processes, is a unique aspect of IASR research.

We are interested in all aspects of the fundamentals of surfactant adsorption.  One focus areas is on the effect of surface geometry on adsorption.   Surface roughness is a form of random horizontal confinement on adsorption.    We have done a number of quartz crystal microbalance studies with surfaces having varying roughness. Surface curvature on a length scale similar to that of a surfactant, such as that found on carbon nanotubes, is another focus area.   A more controlled surface roughness is when e-beam lithography is used to make reproducible troughs and terraces.  All of this work is supported by molecular dynamics simulations.

The study of thermodynamic properties of micellar solutions is an important area of both practical and fundamental interest. The ability of surfactant micelles to bind or solubilize components in aqueous solutions gives these systems the unique properties responsible for many of the processes described in this brochure. Unfortunately, our understanding of the molecular equilibria and dynamic behavior of micellar systems is still fairly primitive.

Active areas of research at IASR include thermodynamic studies of the formation of micelles from individual surfactant molecules, the binding or solubilization of individual compounds or ions by micelles, the crystallization of surfactants, and the prediction of solubilization phenomena with molecular theories or models. All of these studies are fundamental in character, but advances in our knowledge of micellar and solubility properties will relate directly to many types of technological improvement. IASR's experimental and theoretical expertise in the field of surfactant thermodynamics should enable the group to make substantial contributions in this important area of research.

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Surfactant mixtures have numerous synergisms in practical applications. However, the surfactant interactions in these systems are also inherently of great theoretical interest. Interaction between dissimilar surfactants in various aggregation processes is being investigated.

Fundamental models are being developed to describe surfactant mixture effects in specific processes. Experimental data provide a test of these models. It is this type of approach, balancing theory and experimental verification, that IASR is using to advance knowledge in this field.

Our efforts in surfactant synthesis involve preparation of new fluorinated surfactants in connection with our research on perfluorochemical blood substitutes. The goal is to synthesize fluorinated surfactants that will form stable, non-viscous microemulsions containing high contents of fluorocarbons, with very small emulsified particles that are not adsorbed on the surface of red blood cells. The synthetic procedure is straightforward, and the yield is high. Our methods lead to the production of fluorinated surfactants which are free from the toxic impurities that frequently result from conventional syntheses.

We have extensively explored extended surfactants.     Surfactants normally have a hydrophobic alkane tail and a hydrophilic head; in extended surfactants a group that is less hydrophobic then an alkane and less hydrophilic then a typical hydrophilic head is inserted.   The most common insertion moiety is a few repeat units of propylene oxide; often followed by ethylene oxide which in turn is typically sulfated.   Such surfactants form microemulsions at room temperature much more easily with a variety of oils than most normal surfactants.  

Another unique surfactant type we have studied are double tail surfactants including gemini surfactants.    The most common of these we have studied has been sodium dioctyl sulfosuccinate, which is often given the abbreviation AOT (the abbreviation comes from AerosolĂ” OT, with OT standing for octyl).   AOT is another surfactant that is very good for making microemulsions, as well as using as a reference surfactant when trying to determine properties of other surfactants for help in designing microemulsions. 

Finally, sulfoxide surfactants has been a more recent focus of the center.   We have done significant fundamental work in characterizing just how hydrophilic the sulfoxide head group really is; the answer is that this head group is very hydrophilic!   Also, these surfactants behave like typical nonionic surfactants when examining their salt tolerance for example, but changes in properties with temperature more closely resemble ionic surfactants.  


Microemulsions are a critical piece in a number of different application areas, including prewash detergency, enhanced oil recovery and hard surface cleaners.  Our group has developed rapid screening and predictive capabilities to be able to formulate a microemulsion with an arbitrary surfactant, with particular focus on middle-phase microemulsions because of their ultra-low interfacial tensions.   A particular focus of our group has been designing microemulsions with very difficult to formulate vegetable oils, both because these are very difficult to clean and because microemulsions are a way to lower viscosity for engines based on vegetable oil.   We have also contributed greatly to fundamental understanding of the morphology and solubilization capacities of these morphologies.