Heteropoly acids (HPA)s are a large class of inorganic acids that are known to have extremely high proton conductivities.[1] It has been demonstrated that doping perfluorinated sulfonic acid and hydrocarbon-based membranes with HPA is able to improve protonic conductivity, particularly under reduced humidity and elevated temperatures, but this method suffers from a lack of stability to water.[2,3] Even when the cesium salt (water-insoluble) is used, it is likely that agglomeration will occur overtime, as the HPA is not truly immobilized. Silicotungstic acid (SiW12O40 -4) is of particular interest for use in a fuel cell because it has been shown to be stable under relevant conditions.[4] In an effort to mitigate agglomeration and water instabilities that plague most HPA containing films, we have covalently attached silicotungstic to 3M FC-2145 (polyvinylidene-co-hexafluoropropylene), forming a highly crosslinked polymer/hybrid network. First, phenol phosphonic acid (PPA) side chains are attached to FC-2145, and then two PPA groups react with a single, mono-lucunary silicotungstic acid (SiW11O39 -8), thus forming covalent crosslinks. This synthesis produces materials that have loadings of HPA, stable to boiling, in excess of 60wt%. The resulting material has high proton conductivity (>200 mS/cm at 90°C/95%RH) under humidified conditions as well as relatively high proton conductivity (>30mS/cm at 110°C/50%RH) under lower humidity conditions. This talk will include discussion on synthesis, transport properties, and preliminary chemical stability.