title: Transitional phase inversion of emulsions monitored by in situ near-infrared spectroscopy.
abstract: Water-heptane/toluene model emulsions were prepared to study emulsion transitional phase inversion by in situ near-infrared spectroscopy (NIR). The first emulsion contained a small amount of ionic surfactant (0.27 wt % of sodium dodecyl sulfate) and n-pentanol as a cosurfactant. In this emulsion, the study was guided by an inversion coordinate route based on a phase behavior study previously performed. The morphology changes were induced by rising aqueous phase salinity in a "steady-state" inversion protocol. The second emulsion contained a nonionic surfactant (ethoxylated nonylphenol) at a concentration of 3 wt %. A continuous temperature change induced two distinct transitional phase inversions: one occurred during the heating of the system and another during the cooling. NIR spectroscopy was able to detect phase inversion in these emulsions due to differences between light scattered/absorbed by water in oil (W/O) and oil in water (O/W) morphologies. It was observed that the two model emulsions exhibit different inversion mechanisms closely related to different quantities of the middle phases formed during the three-phase behavior of Winsor type III.
authors: Programa de Engenharia Química, COPPE, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
authors: R M
authors: RM
authors: Charin
authors: M
authors: M
authors: Nele
authors: F W
authors: FW
authors: Tavares
mesh_terms: D004655:Emulsions / Q000737:chemistry; D006536:Heptanes / Q000737:chemistry*; D019265:Spectroscopy, Near-Infrared; D013501:Surface-Active Agents / Q000737:chemistry; D014050:Toluene / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
chemical_list: D004655:Emulsions; D006536:Heptanes; D013501:Surface-Active Agents; D014867:Water; D014050:Toluene