SHEAR EFFECTS ON SOLVATED BLOCK-COPOLYMER LAMELLAE - POLYSTYRENE-POLYISOPRENE IN DIOCTYL PHTHALATE

Small-angle neutron scattering experiments were performed on a polysty rene-polyisoprene diblock copolymer in concentrated dioctyl phthalate solution under Couette shear. Lamellar orientations were monitored bel ow and above the order-disorder transition temperature with the neutro n beam incident either radially or tangentially on the cylindrical she ar cell. It was found that lamellae are oriented mostly parallel to th e plane of the shear cell walls. Oscillatory shear helps improve the l amellar alignment. Above the quiescent order-disorder transition, the shear-induced alignment (observed as an anisotropy of the scattering r ing) follows a master curve for all temperatures.