Light-scattering investigations on dilute nonionic oil-in-water microemulsions
- 1 June 2000
- journal article
- Published by Springer Nature in AAPS PharmSci
- Vol. 2 (2) , 16-26
- https://doi.org/10.1208/ps020212
Abstract
Dilute 3-component nonionic oil-in-water microemulsions formulated with either a polyoxyethylene surfactant (C18∶1E10 or C12E10) or the alkylamine-N-oxide surfactant, DDAO (C12AO), and containing either a triglyceride or an ethyl ester oil have been examined using dynamic and static light-scattering techniques. Analysis of the results showed distinct differences in the tested oils mode of incorporation into the microemulsion droplets, with both the molecular volume of the oil and the hydrophobic chain length of the surfactant being important. For example, microemulsions formulated by C18∶1E10 and containing one of the larger molecular volume oils (that is, either a triglyceride, Miglyol 812, or soybean oil) or the ethyl ester of fatty acid oil, ethyl oleate, exhibited first a decrease and then an increase in hydrodynamic size and surfactant aggregation number, suggesting that the asymmetric C18∶1E10 micelles became spherical upon the addition of a small amount of oil and grew thereafter because of further oil being incorporated into the core of the spherical microemulsion droplet. A similar conclusion of sphericity could not be drawn for microemulsions stabilized by C18∶1E10 and containing one of the oils smaller in molecular volume (namely tributyrin, ethyl butyrate, or ethyl caprylate) where neither the aggregation number nor the hydrodynamic radius changed much upon the addition of oil. This result suggested that these oils were preferentially located in the interfacial surfactant monolayer, behaving in much the same way as a cosurfactant. A different trend of results, however, was seen for microemulsions prepared using C12E10 and C12AO, most likely because these surfactants produced approximately spherical micelles. In this case, the microemulsions containing the oils larger in molecular volume tended to exhibit an increase in surfactant aggregation number and hydrodynamic size, suggesting the growth of spherical micelles, while the smaller oils (in particular ethyl butyrate) caused a significant decrease in surfactant aggregation number incompatible with their being incorporated into the centre of the droplet, suggesting that the oils were being located in the interfacial surfactant monolayer. These results suggest that the various oils are incorporated into the microemulsions in very different ways.Keywords
This publication has 12 references indexed in Scilit:
- Nonionic surfactant phase behavior. The effect of CH3 capping of the terminal OH. Accurate measurements of cloud curvesPublished by Springer Nature ,2008
- The aggregation behaviour of tetradecyldimethylaminoxidePublished by Springer Nature ,2007
- Nonionic oil-in-water microemulsions: the effect of oil type on phase behaviourPublished by Elsevier ,2000
- Effect of Oil on the Level of Solubilization of Testosterone Propionate into Nonionic Oil-in-Water MicroemulsionsJournal of Pharmaceutical Sciences, 1998
- Aggregation and Surface Properties of Synthetic Double-chain Non-ionic Surfactants in Aqueous SolutionJournal of Pharmacy and Pharmacology, 1997
- Three-component non-ionic oil-in-water microemulsions using polyoxyethylene ether surfactantsColloids and Surfaces B: Biointerfaces, 1995
- Light scattering - diagnostic methods for colloidal dispersionsAdvances in Colloid and Interface Science, 1993
- A comparison of the incorporation of model steroids into non-ionic micellar and microemulsion systemsJournal of Pharmacy and Pharmacology, 1993
- Micelle formation of pure nonionic surfactants and their mixturesLangmuir, 1992
- Analysis of Macromolecular Polydispersity in Intensity Correlation Spectroscopy: The Method of CumulantsThe Journal of Chemical Physics, 1972