Suspensions of Silica Particles Grafted with Concentrated Polymer Brush:  A New Family of Colloidal Crystals

A colloidal crystal was newly identified for a liquid suspension of the hybrid particles having a spherical silica core and a shell of well-defined poly(methyl methacrylate) “concentrated brush”. With increasing particle concentration, the suspension progressed from a (disordered) fluid to a fully crystallized system, going through a narrow crystal/fluid coexisting regime. The crystal had a face-centered cubic structure with a surprisingly large nearest-neighbor interparticle distance, suggesting that the graft chains, highly extended due to the “concentrated brush effect”, exerted a long-range steric interaction. This type of colloidal crystal is new with respect to the origin of long-range interparticle potential and the controllability of many of the system parameters.