Small-angle Neutron Scattering Analyses of Nanoemulsion

Abstract

A stable nanoemulsion consisting of nanometer-sized oil droplets in water having a self-standing capability was prepared by high-pressure emulsification. Rheological measurements show that the nanoemulsion has a yield stress. Small-angle neutron scattering (SANS) revealed the presence of an ordered crystal-like lattice structure in addition to spherical domains with a radius of 17 nm.

A mixed solution of 2-hydroxyethyl cellulose and dilution of the nanoemulsion has shear-thickening behavior (shear-induced gelation). Real-time SANS measurements with a Couette geometry as a function of shear rate showed an increase in the scattering intensity exclusively at low scattering angle region. However, neither aggregation nor deformation of droplet was detected and the SANS patterns remained isotropic irrespective of shear rate. A possible mechanism of gelation is proposed from the viewpoint of shear-induced percolation transition.