Contents lists available at ScienceDirect Colloids and Surfaces A journal homepage: www.elsevier.com/locate/colsurfa Characterization of reverse microemulsion formed with functionalized surfactants based on ferrycianide ions Fernando Martínez-Martínez a , Alberto Gutiérrez-Becerra b , Norberto Casillas a , Michael Gradzielski c , José I. Escalante a , Maximiliano Bárcena-Soto a, ⁎ a Department of Chemistry, University of Guadalajara, Blvd. M. García Barragán 1451, Guadalajara, 44430, Mexico b Department of Basic and Applied Sciences, and Engineering, University of Guadalajara, CUTonala, Av. Nuevo Periférico 555, Tonalá, 45425, Mexico c Stranski-Laboratorium für Physikalische und Theoretische Chemie, Institut für Chemie, Technische Universität Berlin, Straße des 17 Juni 124, Sekr. TC7, D-10623, Berlin, Germany GRAPHICAL ABSTRACT ARTICLE INFO Keywords: Reverse microemulsions Functionalized surfactant Ferricyanide Schulman’s titrations ABSTRACT Schulman's titration (ST) and dynamic light scattering (DLS) were employed to obtain structural parameters of the reverse microemulsions formed by the functionalized surfactants cetyltrimethylammonium ferricyanide (CTAFeIII) and didodecyldimethylammonium ferricyanide (DDAFeIII). From the ST, the amount of surfactant and cosurfactant per droplet can be calculated, and if the droplets are spherical, it is possible to determine the droplet radius taking into account geometrical parameters. DLS measures the collective diffusion coefficient of the droplets, and then by means of the Stoke-Einstein equation, the droplets radius can be calculated. When the amount of water in the microemulsions is lower than 15 wt%, both techniques yield similar droplet radii, re- gardless of the functionalized surfactant used, which indicates that the microemulsions contain spherical dro- plets in this range of water concentration. When the amount of water reaches 20 wt% the radii obtained by DLS are larger than the one deduced from ST, suggesting that at this water concentration, the droplets are not https://doi.org/10.1016/j.colsurfa.2018.01.024 Received 4 November 2017; Received in revised form 9 January 2018; Accepted 10 January 2018 ⁎ Corresponding author. E-mail address: maximiliano.barcena@cucei.udg.mx (M. Bárcena-Soto). Colloids and Surfaces A 541 (2018) 10–16 Available online 11 January 2018 0927-7757/ © 2018 Published by Elsevier B.V. T