Shear-induced order in aqueous micellar solutions of amphiphilic poly(tert-butylstyrene)-b-poly(Na methacrylate) diblock

Shear-induced order of aqueous micellar solutions of a poly(tert-butylstyre ne)-b-poly(sodium methacrylate) diblock (c = 2.5-15 w/v %) has been investi gated by small-angle X-ray scattering. Data collected from a Couette cell i n both radial and tangential geometries agree with a crystalline ordering o f micelles in close packed hexagonal lavers perpendicular to the velocity g radient, when c is in the 5-10 w/v % range. The measured interlayer distanc e is indeed very close to the value expected for a close-packed structure. The experimental data are consistent with a zigzag motion of adjacent plane s upon shear. Shear-induced order is, however, restricted to a narrow conce ntration range just above the concentration for the sol-gel transition. Thi s domain is thought to correspond to a regime where relative layer translat ion modes are allowed whereas mutual rotation is hindered.