Admicellar Polymerization

Surfactant micelles are known to anyone who has washed dishes or themselves (which I hope is everyone!).  Almost all food or dirt is composed of organic matter, in other words it is oil-like. Therefore, just like oil and water don’t mix very well, water without soap (the active ingredient in soap is surfactant) will not wash your dishes or yourself very well, no matter how hard you try to convince your mother otherwise. So you add soap to water, and by doing this you can clean whatever it is you wish to clean.

How does this work, i.e. how does surfactant clean.  Surfactants are molecules that have an oil-like part and a water like part on the same molecule, as shown in the Figure to the right. The green circle is the water-like part, while the yellow jagged line is the oil-like part. A typical water-like part is SO₄^-Na⁺ while a typical oil-like part is composed of 10-20 repeating CH₂ units. When you put these molecules in water, you get many different organizations of these molecules in the water depending on the packing factor (F) which is defined as F=v/aoLc.The possible organizations are shown
in the Table below.

In terms of soap, micelles are the important morphology; what happens is that the dirt or food segregates to the inside of the micelles, and is carried away by the running water see Figure 2. If you replace the dirt or food as shown in Figure 2 with monomer, and then polymerize the monomer, you will end up with an emulsion polymer, which is more commonly known as latex paint. In other words, when you paint your walls you are using the same underlying process that you use when you wash your dishes (that's odd, isn't it!!!).

Now in terms of what we are doing, it turns out that the surface analogue of the arrangements in the Table above occur when surfactants adsorb to surfaces.  The arrangements listed in the Table have been known for a long time; however, the fact that these types of arrangements occur at surfaces has been known only since 1995.  Figure 3 below shows the morphologies of surfactants adsorbed at an interface.
                                                                                                                                                                                                                      

What we can do is to use these adsorbed aggregates as reaction templates, i.e. adsorb a monomer to the interior of the adsorbed aggregates, and allow the monomer to react. This process was discovered approximately 15 years ago at OU and is termed admicellar polymerization. Research concerning surfactant adsorption, admicelles, adsolubililization and reactions within admicelles has progressed steadily in the last 15 years. The work has expanded to include a wide variety of substrates, surfactants, adsolubilizates, reactions and reagents. The fundamentals and possible applications of admicellar polymerization have been and continue to be examined. A few of these fundamentals and applications are discussed in these webpages; consult the references listed below for more information.

The projects on conductive composites and structural composites both utilize admicellar polymerization.  Using this technology, we are able to put a very thin layer of polymer on the surface of either a particulate or fibrous solid, and change the behavior of the material at the polymer-solid interface. In the project on conductive composites, we are able to improve electron transfer across the particle-particle interface which increases the conductivity of the composite. In structural composites we are able to improve polymer-filler adhesion and hence get better mechanical properties.

We have also recently begun more fundamental work. We have addressed the question: Is it possible to transfer the morphologies shown in Figure 3 to the polymer. Specifically, we have used the cylindrical and hemi-cylindrical morphologies to produce polymer wires as shown in Figure 4. We call these structures wires because we have formed an electrically conducting polymer, polyaniline, to form these structures. Hence, we believe this technique might be a way to pattern wires on the surface of atomically flat solid, i.e. single crystal silicon as is used in semiconductor manufacture. We have not yet published this result, but the pictures sure are pretty neat.

See the webpage on nanostructures to see how we use admicellar polymerization along with templated surfaces to create unique polymer nanostructures.

 

 

Relevant References

W.B. Genetti, W.L. Yuan, B.P. Grady, E.A. O'Rear, C.L. Lai and D.T. Glatzhofer, "Polymer Matrix Composites: Conductivity Enhancement through Polypyrrole Coating of Nickel Flake", Journal of Material Science, 33, 3085 (1998).

B.P. Grady, E.A. O'Rear, L. Penn and A. Pedicini, "Admicellar Polymerization of Styrene-Isoprene on Glass Cloth for Use in Composite Manufacture" Polymer Composites, 19, 579 (1998).

H.J. Barraza, M.J. Hwa, K. Blakely, E.A. O'Rear, and B.P. Grady, "Wetting Behavior of Elastomer-Modified Glass Fibers", Langmuir, 17, 5288 (2001).

J.H. O'Haver, B.P. Grady, E.A. O'Rear and J.H. Harwell, "Admicellar Polymerization", in Reactions and Synthesis in Surfactant Systems (Surfactant Science, Vol. 100), J. Texter ed. (New York, Marcel Dekker) 2001.

W. Yuan, E.A. O'Rear, B.P. Grady and D.T. Glatzhofer, "Nanometer-Thick Polypyrrole Films Formed by Admicellar Polymerization under Conditions of Depleting Adsolubilization", Langmuir, 18, 3343 (2002).

K. Bunsomit, R. Magaraphan, E.A. O'Rear and B. P. Grady, "Polypyrrole-Coated Natural Rubber Latex by Admicellar Polymerization", Colloid and Polymer Science, 280, 509 (2002).

X. Wei, A.D.W. Carswell, W. Alvarez and B.P. Grady, “X-ray Photoelectron Spectroscopic Studies of Hydrophilic Surfaces Modified via Admicellar Polymerization, Journal of Colloid and Interface Science, 264, 296 (2003).

A.D.W. Carswell, E.A. O’Rear, B.P. Grady, “Adsorbed Surfactants as Templates for the Synthesis of Morphologically Controlled Polyaniline and Polypyrrole Nanostructures on Flat Surfaces: From Spheres to Wires to Flat Films”, Journal of the American Chemical Society, 125, 14793 (2003).

K. Blakely, B.P. Grady, H.J. Barrazza and E.A. O'Rear, “Effects of Styrene-Isoprene Copolymer Glass Fiber Coatings on Woven Glass Cloth Epoxy Composite Performance”, Polymer Composites, 25, 82 (2004).

P. Lekpittaya, N. Yanumet, B.P.Grady, and E.A. O’Rear, “Resistivity of Conductive Polymer-Coated Fabric”, Journal of Applied Polymer Science, 92, 2629 (2004).

P. Rungruang, B.P. Grady and P. Supaphol, “Surface-Modified Calcium Carbonate Particles by Admicellar Polymerization to be used as Filler for Isotactic Polypropylene, Colloids and Surfaces A: Physicochem. Eng. Aspects, 275, 114 (2006).

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