A series of designed interphases was produced by grafting chemically modified poly (aryl ether sulfones) (PSF) onto bioactive glass (BAG) particles. Macromolecular architecture, polymer morphology, composition and crosslink density of these PSF hybrid interphases were studied with respect to influence on mechanical properties. The hybrid PSF interphases improved mechanical strength by 20% over conventional silane treatments and increased the overall energy to failure by nearly 100%. The structure of the interphase was modeled with a three-phase viscoelastic model. The results demonstrated the ability to engineer an interphase having hyperstructures containing mobile species and inorganic functionalities that improve adhesion and favor energy release during fracture processes. (c) 2005 Wiley Periodicals, Inc.