SHEAR ORIENTATION OF A LAMELLAR LYOTROPIC LIQUID-CRYSTAL

Shear orientation of a lyotropic lamellar liquid crystalline phase of tetra ethyleneglycol mono dodecylether, C(12)E(4), in water was studie d by combined rheo-small-angle light scattering. Shear thinning was ob served with a sample of 500 mu m thickness. The scattering patterns sh owed 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 scatt ering vector with increasing shear stress. This observation can be exp lained by a fragmentation of domains at high shear stress and is suppo rted by a mosaic texture observed in optical microscopy.