Shear orientation of a lamellar lyotropic liquid crystal

Shear orientation of a lyotropic lamellar liquid crystalline phase of tetra ethyleneglycol mono dodecylether, C₁₂A₄ in water was studied by combined rheo-small-angle light scattering. Shear thinning was observed with a sample of 500 m thickness. The scattering patterns showed that domains were aligned and stretched in flow direction. Shear thinning was also observed with a thinner sample, but caused a strong change in light-scattering pattern. A maximum of scattering intensity was observed at finite scattering vector and shifted to a higher scattering vector with increasing shear stress. This observation can be explained by a fragmentation of domains at high shear stress and is supported by a mosaic texture observed in optical microscopy.