8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

P7.68Thu 811:10-14:00Surface-induced self-assembly of surfactants inconfinementDirk Müter, 1 Tae Gyu Shin, 2 Oskar Paris, 3 and Gerhard H. Findenegg 41 University of Copenhagen, Department of Chemistry, Universitetsparken 5 2100,Copenhagen, Denmark2 Hanyang University, Seoul, South Korea3 Montanuniversität Leoben, Leoben, Austria4 Technische Universität Berlin, Berlin, GermanySurfactant self-assembly plays an important role in a range of everyday applications but the structuralproperties of those assemblies can be affected decisively when subjected to a confined geometry.Surfactant aggregation in narrow pores is of particular importance to the environmentaland pharmaceutical industry. We have studied the surface-induced aggregation of non-ionic surfactants(C 10 E 5 and C 12 E 5 ) in a strongly confined geometry of cylindrical nanopores. An orderedmesoporous silica material constituting 2-d hexagonal arrays of cylindrical pores of 8 nm diameterwas used as the matrix. The morphology of surface aggregates of surfactants in the pores wasstudied by small-angle neutron scattering (SANS). Experiments were performed in a mixture ofH 2 O and D 2 O matching the neutron scattering length density of the silica matrix as well as inpure D 2 O. The scattering profiles were fitted with the analytical model introduced in [1] whichallows retrieving complementary structural information about the surfactant aggregates from thediffuse and Bragg scattering contributions. In this model the diffuse scattering is described by theTeubner-Strey formalism for correlations between individual aggregates while the Bragg peaks areutilized in a form factor model for the adsorbed surfactant film. In order to evaluate the scatteringdata from pure D 2 O as well we generalized this part of the model [2] by introducing a two-stepdensity distribution to account for the higher scattering length density. This enhanced model functionyields excellent fit quality and enables us to follow the growth of the surfactant film in bothcontrast scenarios as well as the change in density for pure D 2 O and shows that the cylindricalconfinement has a distinct effect on the ultimate thickness of the surfactant film.[1] Müter, Shin, Demé, Fratzl, Paris, Findenegg, JPC Lett. 1, 1442-6 (2010).[2] Shin, Müter, Meissner, Paris, Findenegg, Langmuir, doi: 10. 1021/la200333q (2011)68