Polymeric particles with hydrophobic PCL hairy chains were prepared by ring-opening polymerization (ROP) from hydrophilic core particles, which were prepared by soap-free emulsion polymerization of styrene, 2-hydroxyethyl methacrylate, and divinylbenzene. Due to the incorporation of 2-hydroxyethyl methacrylate in the core particles, hydroxyl groups on the surface of core particles could be obtained, and in the following ROP of a-caprolactone, the hydroxyl groups on the surface of the particles could effectively initiate the polymerization. Various reaction conditions were evaluated to produce hairy particles with optimal grafting efficiency. The presence of hydrophobic polymeric hairs on the surface of particles led to a dramatic improvement in their dispersibility in oil phase. By controlling the grafting amount of PCL on the surface of hydrophilic core particles, the surface properties of the hairy particles could be well tailored, represented the change of water contact angles from 75.0 to 114.6. The prepared hairy particles were characterized by thermogravimetric analysis, scanning electron microscopy, differential scanning calorimetry, and Fourier transform infrared analysis. (c) 2007 Wiley Periodicals, Inc.