title: Kinetics of Oil Exchange in Nanoemulsions Prepared with the Phase Inversion Concentration Method.
abstract: Nanoemulsions (NEs) are metastable emulsions with droplet sizes between 20 and 100 nm and with a wide range of applications, for example, in polymerization, in pharmaceutical and cosmetic formulations, and as drug delivery systems. Even though they are not in thermodynamic equilibrium, they can be metastable over relatively long times and have the advantage that they can be formed easily by low energy input methods. In particular, the phase inversion concentration (PIC) method allows the formation of NEs by the dilution of a suitable mixture of oil and surfactants with water. In this paper, we investigate the kinetics of the oil exchange process of NEs formed by the PIC method by looking at the exchange of different hydrophobic oils and by employing contrast variation stopped flow small-angle neutron scattering. These experiments demonstrate that this exchange becomes substantially slower by increasing the chain length of the alkane. This indicates a mechanism where monomer exchange is relevant, which would indicate also that for aging one would expect Ostwald ripening to be the determining factor. Such investigations can be carried out in a unique fashion by means of neutron scattering, and the results have important implications for the optimization of NE formulations.
authors: Stranski-Laboratorium für Physikalische und Theoretische Chemie, Institut für Chemie, Technische Universität Berlin , Straße des 17. Juni 124, Sekr. TC 7, D-10623, Berlin, Germany.|Institut Max von Laue-Paul Langevin (ILL) , F-38042 Grenoble Cedex 9, France.
authors: Ingo
authors: I
authors: Hoffmann
authors: Stranski-Laboratorium für Physikalische und Theoretische Chemie, Institut für Chemie, Technische Universität Berlin , Straße des 17. Juni 124, Sekr. TC 7, D-10623, Berlin, Germany.
authors: Miriam
authors: M
authors: Simon
authors: Stranski-Laboratorium für Physikalische und Theoretische Chemie, Institut für Chemie, Technische Universität Berlin , Straße des 17. Juni 124, Sekr. TC 7, D-10623, Berlin, Germany.
authors: Anja
authors: A
authors: Hörmann
authors: Stranski-Laboratorium für Physikalische und Theoretische Chemie, Institut für Chemie, Technische Universität Berlin , Straße des 17. Juni 124, Sekr. TC 7, D-10623, Berlin, Germany.
authors: Thorsten
authors: T
authors: Gravert
authors: Stranski-Laboratorium für Physikalische und Theoretische Chemie, Institut für Chemie, Technische Universität Berlin , Straße des 17. Juni 124, Sekr. TC 7, D-10623, Berlin, Germany.|Institut Max von Laue-Paul Langevin (ILL) , F-38042 Grenoble Cedex 9, France.
authors: Peggy
authors: P
authors: Heunemann
authors: ISIS , Rutherford Appleton Laboratory, Harwell Oxford, Didcot OX11 0QX, U.K.
authors: Sarah E
authors: SE
authors: Rogers
authors: Stranski-Laboratorium für Physikalische und Theoretische Chemie, Institut für Chemie, Technische Universität Berlin , Straße des 17. Juni 124, Sekr. TC 7, D-10623, Berlin, Germany.
authors: Michael
authors: M
authors: Gradzielski