ABS/layered silicate nanocomposites were synthesized through an emulsion polymerization with different sizes of silicates. The particle sizes of Laponite, Cloisite-Na and Kunipia-F are about 20-30, 70-150, and 300-500 nm, respectively. When ABS was synthesized by the emulsion polymerization in the presence of Laponite and Cloisite-Na, ABS/layered silicate nanocomposite emulsion showed a stable suspension without the precipitation of solid particle. On the other hand, ABS/layered silicate nanocomposite synthesized with Kunipia-F showed the precipitation of large aggregated particles and the phase separation. Smaller sizes of silicates like Laponite and Cloisite-Na than polymerized particle worked as resided barrier preventing the emulsion particle from coagulation. Larger size of silicate like Kunipia-F than emulsion particle was not able to enclose the emulsion particle delicately because of its stiffness and large aspect ratio. The monomers inserted into the intercalated Kunipia-F connected the ABS particles and clay particles. The Kunipia-F particles anchored ABS particles around them inducing the aggregation and precipitation of ABS particles. ABS copolymer emulsion and aqueous silicate dispersion were mixed to compare with synthesized ABS/layered silicate nanocomposites and showed a stable suspension. With small amount of Laponite or Cloisite-Na, nanocomposite emulsion of Kunipia-F was also stabilized. Laponite and Cloisite-Na worked as a steric stabilizer. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 119: 1287-1296, 2011