Intermediate structures in equilibrium flocculation

Abstract Small-angle neutron scattering is used to determine the organization of silica particles which have been dispersed in water and covered with adsorbed poly(ethylene oxide) macromolecules. Aggregates are formed when the range of bridging attractions exceeds that of electrostatic repulsions. When the repulsions are still strong the aggregates are one-dimensional necklace-like structures. Depressing the repulsions allows the necklaces to bind to each other; the aggregates become bushy structures and then three-dimensional gels with liquid-like short-range order.