Ripening of Nonaqueous Emulsions of n-Decane in Dimethyl Sulfoxide Observed by Time-Resolved Spin-Echo Small-Angle Neutron Scattering (SESANS)
E. Wouter Grünewald (Student TU Delft)
Robert Dalgliesh (ISIS Neutron and Muon Source)
S.R. Parnell (TU Delft - RID/TS/Instrumenten groep)
W.G. Bouwman (TU Delft - RST/Neutron and Positron Methods in Materials)
Gregory N. Smith (ISIS Neutron and Muon Source)
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Abstract
Since macroemulsions are only kinetically stable, characterizing their behavior as they change over time is relevant to their application. Time-of-flight spin-echo small-angle neutron scattering (SESANS) enables time-resolved measurement of the bulk evolution of concentrated, opaque emulsions without perturbing the system. Here, we present time-of-flight SESANS measurements of an n-decane-in-DMSO emulsion stabilized by Pluronic P-123, where changes in the system as it ripened were resolved. The radius of emulsion droplets were shown to grow over time with a rate of 25 μm3 h–1, suggesting that Ostwald ripening is the dominant aging process. Furthermore, SANS measurements revealed the presence of a stable population of swollen surfactant micelles, providing an additional mechanism for mass transfer between particles. Since time-of-flight SESANS can be used to obtain information about particle sizes, ripening rates, and associated processes, it is uniquely suited for studying the behavior of dense colloidal systems over time.
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