Small-Angle Neutron Scattering Study of Nonionic Surfactant Micelles and Phase Transitions in w/o Microemulsion

Abstract

The structure of micelles formed by a four component water-in-oil nonionic microemulsion surfactant polyoxyethene (20) sorbitan monoleate (Tween 80), sorbitan monolaurate (Span 20) at ethyl oleate and deuterated water interface have been probed by small-angle neutron scattering (SANS). The total surfactant concentration in each of the samples studied (Tween 80: Span 20) is fixed at 3:2. The deuterated water content is variable at 5–60% w/w. The experimental SANS data from all the seven samples are fit well by spherical micelles interacting with hard sphere potential. Increased deuterated water leads to spherical to lamellar and rod-like micelle geometry featured in the SANS scattering data. The observed change in micelle geometry supports the characterization of phase transition between the self-assembled micelles of the nonionic microemulsion.

Keywords:

• Lamellar bilayer
• liquid crystal
• microemulsion
• phase transition
• reverse micelle
• small-angle neutron scattering

ACKNOWLEDGMENTS

The authors thank Solid State Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai, India, for providing the beam time for the SANS experiments.

Notes

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