This manuscript describes a versatile, yet experimentally facile, method for producing libraries of polymer coated (core-shell type) gold nanoparticles. The synthetic principle relies on two, sequential postmodification reactions, which ensures homogeneity across each series. First, poly(pentafluorophenyl methacrylate) synthesized by RAFT polymerization is used here as a reactive precursor, which can be modified, postpolymerization, to create a library of functional polymers each bearing a omega-thiol end-group. In a second step, these well-defined polymers are then tethered by their omega-thiol group to the surface of prefabricated citrate-stabilized gold nanoparticles to give a library of 75 unique, yet sequentially modified organic-inorganic hybrid particles. The optical properties of the gold core were exploited to create a high throughput assay for investigating the role of nanoparticle size and surface coating on aggregation in various biologically relevant media. These experiments demonstrated the importance of the type of dissolved salts present and also the, strong influence of serum proteins in cell culture media and their interactions with nanoparticles surfaces, which in turn might affect I their biological profiles Therefore, this method presents a powerful, yet accessible tool for creating model nanoparticle libraries with intrinsic sensing properties.