| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 594254 | Colloids and Surfaces A: Physicochemical and Engineering Aspects | 2012 | 6 Pages |
Polyethoxylated alkyl compounds consist in a surfactant class that, apart from having a broad application in many fields, yields self-assembled clusters with peculiar geometries: the worm-like micelles. In this work a microemulsion consisting of xylene, water, butanol, and nonaethyleneglycol-monododecylether was studied using rheometry and dynamic light scattering. Zero-shear rate viscosity-temperature dependence had a peculiar Arrhenius character, with the occurrence of two apparent flow activation enthalpies, a higher one below 25 °C, and a lower one above this very temperature. KWW equation was fitted to intensity correlation function data obtained from dynamic light scattering experiments at different temperatures. The temperature dependence of KWW-related parameters indicated that the change in flow activation enthalpy could be related to a change in micelle morphology.
Graphical abstractA drastic change in apparent flow activation enthalpy (the slope of lnη0versus 1/T curve) indicates a transition between nanodrop/worm-like geometries.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Viscosity of a microemulsion has an Arrhenius-type dependence on temperature. ► Arrhenius dependence has two activation enthalpies, above and below a critical temperature. ► DLS suggests relaxation is governed by 2 relaxation rate distributions (2 KWW functions). ► Parameters from KWW equation have abrupt changes above and below same critical temperature. ► Changes related to increase/decrease of worm-like structures as a function of temperature.
