Neutron scattering study on the structure and dynamics of oriented lamellar phase microemulsions

Lamellar phases consisting of water and oil with intervening surfactant monolayer interfaces (eventually containing low molecular weight amphiphilic block-copolymers) are studied. Structural and dynamical investigations of oriented lamellar phases at the length scale of the intermembrane distance and beyond are performed using small-angle neutrons scattering and neutron spin-echo spectroscopy. The data analysis in terms of static and dynamic structure factors for a stack of elastic interfacial membranes yields information of the membrane curvature elasticity and membrane interactions in terms of phenomenological parameters such as the bending elastic modulus $\kappa$ and compression modulus $\overline{B},$ and on the dissipation related to the viscosity $\eta .$ The influence of the block-copolymers anchored to the surfactant monolayers is studied for a series of lamellar phase microemulsions containing equal volume fraction of surfactant and polymer, by varying only the polymer molecular weight. Based on numerical evaluations and fits to the data the conditions of applicability of the available theoretical concepts are discussed.