Restricted swelling and its orientation effect on copolymer micellar solutions of hexagonal-packed cylinders under steady shear flow.

We investigate the structure of polystyrene-b-poly(acrylic acid, sodium salt) copolymer in aqueous solutions. We offer detailed characterization of the micellar solutions by scattering techniques and show that they form hexagonal-packed cylinders. The micelles follow the swelling law expected for cylinders, upon addition of water, down to a concentration threshold below which the distance cylinder-cylinder remains constant. The results suggest that the cylinders are aggregated. It is proposed that this micellar association is the cause of the unusual orientation of the cylinders in a steady shear flow field, where the cylinder axis is found to be parallel to the velocity gradient.