Tuesday, November 16, 2010

Micelle Formation Theory

The following articles describe micelle formation and theoretical aspects. Note several PolyVivo products are capable of forming micelles for drug delivery and other uses. Go to www.polyvivo.com to find out more. Go to original source or links below for full-text of these articles. Abstract follows:

"We predict, qualitatively, the structural transitions in microemulsion systems induced by nonionic polymers, by virtue of their ability to associate with the surfactant assemblies. The predictions are made possible by linking (a) theoretical calculations of the domains of existence of oil-in-water (O/W) and water-in-oil (W/O) droplet microemulsions with (b) the experimental observation that on increasing the alcohol-to-surfactant ratio, an O/W droplet microemulsion phase inverts to a W/O droplet microemulsion, often via a bicontinuous microemulsion. We predict five distinct types of polymer-induced structural transitions: (I) an OIW droplet microemulsion remains an O/W droplet system but the amount of oil solubilized and the radius of the droplet are both reduced; (11) a bicontinuous microemulsion transforms into an O/W droplet microemulsion; (111) a WIO droplet microemulsion inverts to an O/W droplet microemulsion with the droplet radius either decreasing in size (IIIA) or increasing in size (IIIB); (IV) a WIO droplet microemulsion transforms into a bicontinuous microemulsion; (V) a WIO droplet microemulsion remains a W/O system but the droplet radius and the amount of water solubilized are both increased. We also predict that the addition of polymers cannot lead to the following types of transitions: (VI) an OIW droplet microemulsion cannot invert to a W/O droplet microemulsion; (VII) an 01 W droplet microemulsion cannot transform into a bicontinuous microemulsion; (VIII) a bicontinuous microemulsion cannot transform into a W/O droplet microemulsion. From a practical point of view, the above predictions open up aneffective approach to the manipulation of microemulsion structures using nonionic-polymer molecules as additives. "
R. Nagarajan, Polymer-induced structural transitions in microemulsions. Langmuir 9(2) (1993) 369-375. (full-text: http://www.personal.psu.edu/faculty/r/x/rxn/1993-Langmuir-9-p369-375.pdf)

"A thermodynamic model for surfactant binding to polymers in dilute aqueous solution is present. It assumes that the inter- molecular contacts between the polar and the non-polar polymer segment resemble the macroscopic hydrocarbon-water interface ,where preferential accumulation of surfactant accurs. The model also considers the competitive surfactant micelization."
R. Nagarajan, Thermodtnamics of surfactant-polymer interactions in dilute aqueous solutions. Chemical Physics Letters 76(2) (1980) 282-286. (full-text: http://www.personal.psu.edu/faculty/r/x/rxn/1980-Chem%20Phys%20Lett-76-p282-286.doc)
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