Microdomain orientation in chelate-doped block copolymers by a high magnetic field

Magnetic orientation of microdomain structures has been examined for block copolymers consisting of non-crystalline block chains. In order to enhance the effect of the magnetic field, the difference in magnetic susceptibility between the microdomain (dispersed phase) and the matrix phase was increased by doping a metal chelate selectively in the microdomain. A polystyrene-block-poly (ethylene-co-but-1-ene)-block-polystyrene triblock copolymer (SEBS), which forms polystyrene (PS) cylinders in the poly (ethylene-co-but-l-ene) (PEB) matrix, was employed. By solution casting using dichloromethane, a good solvent selectively for PS, non-equilibrium lamellar microdomains were formed and frozen in the as-cast film. The SEBS sample, cast on aluminum foil in the presence of a high magnetic field of 12 T, was then annealed at 190 degrees C for 3 h. The orientation of PS cylinders was examined by small angle X-ray scattering at room temperature. It was found that the lamellar microdomains were oriented parallel to the magnetic field. After annealing, 6-folded pattern appeared, which was ascribed to well-ordered cylinders aligned parallel to the applied magnetic field.