Some fluids can respond to an applied electric fluid, switching from a disordered structure with a fluid-like response to an ordered structure with a solid-like response. These fluids are called electrorheological fluids. These fluids are made of polymeric materials into which colloidal particles are dispersed. When an electrical field is applied, the particles are polarized and become small electrical dipoles. If the field exceeds a certain threshold, these dipoles attract each other and assemble into chains that are aligned along the field direction.

We show that electric field induced ordering of dielectric nanoparticles in a polymeric liquid is a potential fabrication means to assemble nanoparticles-polymer composites. The resulting composite material consists of a quasi 1–3 connectivity pattern due to the formation of chains by the nanoparticles. The degree to which these rows form is strongly dependent on both the magnitude and frequency of the applied field.

A critical feature in the performance of such fluids is the control of interparticle interactions. We report a real-time, Small Angles Neutrons Scattering and dynamic rheological measurements study of the evolution of structure in a electrorheological fluid during the particles ordering. When an electrical field was applied, a two-dimensional set of diffraction spots was obtained, located in the direction of chain alignment. The spacing of these diffraction spots yields the average interparticle distance, which is found to vary with the electrical field, the field frequency and the surface chemistry of the nanoparticles.