Stable translucent aqueous suspensions of azide-functionalized cross-linked nanoparticles (NPs), with diameters in the 15-20 nm range, were prepared using two synthetic approaches. Copolymerization of azidomethylstyrene (VBN(3)), styrene, and divinylbenzene in various oil-in-water microemulsions led to NPs with modulable azide contents (0.53-0.78 mmol/g) and surface over volume distributions. Surface modifications of reactive NPs bearing chlorobenzyl groups, produced by microemulsion copolymerization of vinylbenzylchloride, with sodium azide led to azido-coated NPs with high densities of peripheral groups (0.13-0.45 mmol/g). It is shown that the nature of the surfactant used for the preparation of the microemulsion has an impact on the incorporation of VBN3 in the polymer particles as well as on the surface reaction yield. The azide-functionalized NPs were used as clickable polymeric scaffolds for the grafting of sparingly water-soluble dansyl and fluorescein derivatives through copper(I)-catalyzed azide-alkyne cycloaddition in water in the presence of surfactants as solubilizing agents to produce fluorescent NPs. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 50: 314-328, 2012