Nonequilibrium structure of the homogeneous phase of block copolymers under steady flow

Abstract

A theory is developed to describe the scattering function of a diblock copolymer in the presence of a steady homogeneous flow field. The nonequilibrium steady state under flow conditions is analyzed within a mean field approximation that is expected to accurately describe the disordered phase of block copolymer melts. In the absence of flow the theory reduces to the equilibrium theory of Leibler. Simple shear and extensional flows are seen to render the scattering function highly anisotropic and to attenuate the peak intensity. The instability at the spinodal is predicted to disappear for very strong flows, such as a uniaxial extensional flow. The theory provides an expression for the structure factor that will allow for quantitative interpretation of neutron and x-ray scattering experiments on diblock melts under steady macroscopic flow.