  A nonequilibrium molecular dynamics computer simulation on microsegregated
solutions of symmetrical diblock copolymers is reported. As the polymer
concentration increases, the system undergoes phase transitions in the
following order: body centered cubic (BCC) micelles, hexagonal (HEX) cylinders,
gyroid (GYR) bicontinuous networks, and lamellae (L), which are the same
morphologies that have been reported for block copolymer melts. Structural
classification is based on the patterns of the anisotropic static structure
factor and characteristic 3-dimensional images. The systems in the BCC micellar
($\rho\sigma^{3}=0.3$) and HEX cylindrical ($\rho\sigma^{3}=0.4$) phases were
then subjected to a steady planar shear flow. In weak shear flow, the
segregated domains in both systems tend to rearrange into sliding parallel
close-packed layers with their normal in the direction of the shear gradient.
At higher shear rates both systems adopt a perpendicular lamellar structure
with the normal along the neutral direction. A further increase in the shear
rate results in a decrease in lamellar spacing without any further structural
transitions. Two critical shear rate values that correspond to the demarcation
of different structural behaviors were found.
