We present a comprehensive study of the interaction of spherical polyelectrolyte brushes (SPBs) with cationically modified polyacrylamide (CPAM), calcium carbonate (CaCO3) particles, and cellulose fibers. A link to the use of this system as a model for retention aids in the papermaking process is elaborated. Anionically functionalized SPBs with a high cation exchange capacity (CEC) are used together with CPAM as a model system for fiber flocculation and deposition of CaCO3, which are integral steps in the papermaking process. The flocculation efficiency is tested by means of a dynamic drainage jar. Field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) are used to analyze the system, the structure of the agglomerated flocs, and the mechanism of floc formation. The data suggest that the flocculation efficiency can be attributed to the high CEC of SPB in combination with the flexibility of grafted polyelectrolyte chains. FESEM images and AFM support the model of anionic SPBs acting as a particle bridge between fibers and CaCO3. (c) 2006 Wiley Periodicals, Inc.