Polydimethylsiloxane-acrylate/organophilic montmorillonite (PDMS-ACR/OMMT) nanocomposite emulsions were prepared by the copolymerization between ACR and PDMS/OMMT seeding emulsion, which was prepared beforehand by ring-opening in situ polymerization of octamethyl cyclotetrasiloxane (D-4) intercalated into the interlayer of OMMT modified with dodecylbenzene sulfonate acid (DBSA). OMMT, PDMS/OMMT seeding emulsion, and PDMS-ACR/OMMT nanocomposite emulsions were characterized with X-ray diffraction, FTIR, laser particle size analysis, SEM, and TG; the physical properties of the of PDMS-ACR/OMMT latex films were also characterized including adherence, impact property, bend property, hardness, and water resistance. The results showed that DBSA was intercalated into the interlayer of montmorillonite, and ring-opening in situ polymerization of D-4 could be carried out favorably in OMMT interlayer. The onset weight-loss temperature of PDMS-ACR/OMMT latex films was higher than that of polyacrylate latex film by 44 degrees C. When the addition of the amount of OMMT was 2 wt % in PDMS-ACR/OMMT emulsions, OMMT had been peeled into layered structure and dispersed in the continuous polymer phase, the shape of OMMT was regular and its size was uniform, the physical properties of the latex films were improved obviously. (c) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 118: 63-68, 2010