Vorticity-Aligned Droplet Bands in Sheared Immiscible Polymer Blends Induced by Solid Particles

The spatiotemporal organization of complex fluids under flow can be strongly affected by incorporating solid particles. Here, we report that a monolayer of interfacially active microspheres preferentially wetted by the matrix phase can bridge droplets into vorticity-aligned bands in immiscible polymer blends at intermediate particle concentrations and low shear rates. Strong particle bridging ability and the formation of rigid anisotropic droplet bands with a negligible inertia effect in the Newtonian matrix are suggested to be responsible for the vorticity orientation of droplet bands during slow shear flow, which could be understood based on Jeffery orbit theory in the framework of fluid mechanics and strong confinement effect acted by shear walls and adjacent bands. However, increasing the aspect ratio of particles could restrain the formation of anisotropic bands because of reduced particle coverage and promoted droplet coalescence induced by sharp particle corners, increased and uneven distribution of particle aggregates in the matrix phase, and weakened particle bridging ability.