Phase Diagrams and Self-Assembly Patterns of Mixtures of Ionic Surfactants in Water
By: Eduardo Marques
From: Universidade do Porto
At: Instituto de Investigação Interdisciplinar, Anfiteatro
[2013-02-28]
Amphiphilic molecules are the building blocks of a number of self-assembled nanostructures, from micelles and biomimetic membrane systems, to liquid crystals and microemulsions, comprising also adsorbed monolayers and multilayered films. These colloidal assemblies can be used, for instance, as nanoreactors, templates and molecular transporters in a wealth of current applications. If these molecules also show some type of stimuli-responsive aggregation, further practical relevance is added, e.g. in the rheological control of colloidal materials. In this talk, we will present some examples of our investigations on the aqueous phase behavior and microstructure characterization of a series of mixtures of ionic amphiphiles of opposite charge (cationic/anionic surfactants). These systems are very versatile, with their self-assembly being easily tunable by the choice of molecular structure, temperature and ionic strength [1,2]. For, alkyl chain length mismatch between the two amphiphiles may results in some peculiar features of aggregation, including the coexistence of lamellar liquid crystals, temperature-dependent vesicle-to-micelle transitions, fusion and fission of bilayers and (in ternary systems, with oil) to microemulsion formation [3-5]. For instance, on the dilute region of binary and ternary phase diagrams, spontaneous formation of vesicles is observed, which is interesting both from theoretical and practical viewpoints.
[1] EF Marques, O Regev, A Khan, B Lindman, Adv. Colloid Interface Sci, 2003, 100-102, 83-104.
[2] JC Hao, H Hoffmann, Cur. Op. Colloid Interface Sci. 2004, 9, 279.
[3] BFB Silva, EF Marques, P Linse, U Olsson, J. Phys. Chem. B 2009, 113, 10230.
[4] BFB Silva, EF Marques, U Olsson, R Pons, Langmuir 2010, 26, 3058.
[5] BFB Silva, EF Marques, U Olsson, Soft Matter 2011, 7, 225.