Two reactive shells were polymerized on poly(methyl methacrylate) (PMMA) spheres to improve the compatibility of the spheres with a paint binder. By adjusting the buoyancy of the polymerization medium, PMMA, retroreflective spheres with an average diameter of 600 mu m were successfully modified with a thin cross-linked layer together with an amine functional layer outside on the surface. The cross-linked layer was polymerized by methyl methacrylate and ethylene glycol dimethacrylate by suspension polymerization. After that, a second monomer with functional amine group was polymerized and a functional layer was formed on the surface. The amine groups on the modified spheres can react with the enamine groups of acetoacetate already formulated in the binder and connected the spheres and the paint by chemical bond. The structure of the modified spheres was studied using transmission election microscopy, FTIR, DSC, and other tests.(c) 2005 Wiley Periodicals, Inc.