ABSTRACTPre-formed transition metal oxide clusters with methacrylate ligands were polymerized in the presence of organic co-monomers to form inorganic-organic hybrid polymers. The number of polymerizable ligands and thus the crosslinking density of the hybrid polymers can be varied for a given cluster type by partially exchanging the methacrylate ligands for non-reactive ones. The properties of the hybrid polymers can also be varied by adjusting the conditions of the polymerization reaction, especially by a pre-polymerization procedure. It is shown that the thermal stability of polystyrene crosslinked by Zr6O4(OH)4(OMc)12 is thus greatly improved.