Lamellae Alignment by Shear Flow in a Model of a Diblock Copolymer

A mesoscopic model of a diblock copolymer is used to study the stability of a lamellar structure under a uniform shear ow. We rst obtain the nonlinear lamellar solutions under both steady and oscillatory shear ows. Regions of existence of these solutions are determined as a function of the parameters of the model and of the ow. Finally, we address the stability of the lamellar solution against long wavelength perturbations. 1 Introduction We study a mesoscopic model of a block copolymer to describe the re-orientation of a lamellar structure by an imposed uniform shear ow that is either constant or periodic y Present and permanent address: Materials Research Laboratory, University of California, Santa Barbara, CA 93106. z Permanent address: Department of Physics, National Central University, Chungli 320, Taiwan. 1 in time. This is a rst step towards understanding known phenomenology pertaining to the response of the block copolymer microstructure to shear ows near the isot..