Engineers utilize composites to achieve combinations of properties not found in any single material. In particular, particle-filled polymer-matrix-composites are used in many applications for their ease of processing and low mass with additional specific functionality added by the filler material. However, for many composites, only a small weight percentage of particles can be added before the filler will aggregate, leading to inhomogeneous properties and the deterioration of mechanical strength. Polymer grafted nanoparticles (PGNPs) are a single component nanocomposite wherein each nanoparticle has a covalently grafted corona of polymer chains. The use of PGNPs precludes filler aggregation; however, creating a sufficiently robust material using only PGNPs normally requires long, entangled polymer grafts, a restriction which dilutes the filler and limits the functionality of the composite. In this work, the use of PGNPs with short polymer grafts containing reactive groups that can form covalent crosslinks between particles is investigated. This allows for the creation of nanocomposites with an extremely high filler fraction that are also mechanically robust.