Anisotropic small angle light and neutron scattering from a lyotropic lamellar phase under shear

The influence of shear on the lamellar phase of a semi-dilute solution (36% (w/w)) of tetra ethylenglycol dodecylether (CH3[CH2](11)[OCH2CH2]4OH, C(12)E(4)) in water was investigated by Small Angle Light Scattering (SALS), Small Angle Neutron Scattering (SANS) and theology. A plateau modulus was determined by low amplitude oscillatory shear experiments. A strong scattering peak perpendicular to the flow direction and a small peak along the flow direction were observed in rheo-SANS. The rheo-SALS patterns were also anisotropic. At low shear rates, a four lobe pattern was found in depolarized light scattering (H-V) and scattering perpendicular to the flow direction was observed in polarized scattering (H-H) A butterfly pattern was found in light scattering at high shear rates. The butterfly pattern was stable after cessation of shear, but it was changed by slow shear flow. The scattering data can be explained by a shear induced formation of deformed vesicles and the butterfly pattern might be correlated with an assembly of vesicles disordered in the direction of shear.