Poly(2-vinylpyridine)-silica nanocomposite particles can be efficiently prepared by emulsion polymerization at 60oC using a commercial 20 nm aqueous silica sol as the sole stabilizing agent. Unlike earlier nanocomposite syntheses, TEM studies indicate very high silica aggregation efficiencies (88-99 %). The key to success is to use a suitable cationic azo initiator: in contrast, using an anionic persulfate initiator leads to substantial contamination of the nanocomposite particles with excess silica sol. This cationic azo initiator is electrostatically adsorbed onto the anionic silica sol at submonolayer coverage, which suggests that surface polymerization may be important for nanocomposite formation. The poly(2-vinylpyridine)-silica nanocomposite particles have a well-defined ‘core-shell' morphology, with poly(2-vinylpyridine) cores and silica shells: diameters range from 180 to 220 nm and the mean silica contents range from 27 % to 35 % by mass. Moreover, the 2-vinylpyridine can be partially replaced with either styrene or methacrylic comonomers to produce copolymer-silica nanocomposite particles.