A small-angle neutron-scattering study of shear-induced ordering in the cubic phase of a block copolymer gel

The structure of a diblock copolymer gel subjected to steady shearing has been examined using small-angle neutron scattering(SANS). The poly(oxyethylene) (E)-poly(oxybutylene) (B) diblock E86B10 was found to form a body-centered cubic phase in 0.2 M K2SO4 with a polymer concentration 30 wt % at room temperature. Above a critical shear rate in the range (gamma) over dot = 50-500 s(-1), the sample became macroscopically oriented into a polydomain structure with a [111] direction of the bcc unit cell along the shear direction. The SANS patterns obtained at high shear rates contained reflections from the {110} and {211} planes that intersect along a common [111] direction. Even at the highest shear rate employed, (gamma) over dot = 2.5 x 10(4) s(-1), complete shear melting was not observed (i.e., residual order was present in the SANS pattern).