Small particles have been prepared by means of emulsion polymerization from styrene an ethyl acrylate, using different concentrations of emulsifier. The particle size can be controlled in the range of 45-85 nm. The particle surface was modified by introducing an acetal functionality, suitable for acid catalyzed processes. Surface functionalization was performed in two principally different ways. First, by using an acrylic monomer with acetal functionalities in the polymerization step and, second, by means of a surface grafting technique, using nonacrylic monomers.