Pattern formation and scaling in critical polymer mixtures under simple shear flow

Polymer blends under flow are of profound technological importance. In situ microscopy and small-angle scattering permit detailed studies of such syst ems under simple shear: For phase-separated blends near a critical point of unmixing, homogenization occurs via repeated domain fragmentation, which g ives way to distinct patterns in the strong-shear limit. Data for a variety ; of systems collapse onto universal scaling curves that are in good agreem ent with modern theor ies of nonequilibrium critical phenomena. For strongl y incompatible mixtures, however, the shear response appears to saturate in a manner that may have deep implications for the flow-induced blending of macromolecules.