Narrowly distributed poly (styrene-co-(4-vinylpyridine)) microspheres are facilely prepared by a soap-free emulsion polymerization, and their structures and properties are investigated by TEM, FTIR spectra, DSC, and DLS, respectively. The sizes and glass transition temperatures of the polymeric spheres increase with an increase of 4-vinylpyridine in the reactive system. In addition, these polymeric spheres show good stability in water and a series of organic solvents due to their crosslinked structures. When poly(styrene-co-(4-vinylpyridine)) microspheres are obtained in the reactive system where the weight ratio of 4-vinyl pyridine to styrene is less than 4/6, they can be well dispersed in water as well as in organic solvents such as ethanol, toluene and DMF, and show obvious pH sensitive and organic solvent-sensitive characteristics. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013