Atom transfer radical polymerization (ATRP) of n-butyl methacrylate (BMA) in water-borne media, catalyzed and initiated by CuCl/4,4'-di (5-nonyl)-2,2'-bipyridine (dNbpy) and Ethyl 2-bromopropinate (BrCH3CHCOOC2H5) was conducted. The influence of several factors, such as the amount of surfactant, catalyst, initiator and the reaction time, temperature on the stability of the latexes and the control of the polymerization was investigated. The nucleation mechanism of the latexes, thermodynamic data and activation parameters for the ATRP emulsion polymerization of BMA were also reported. (c) 2005 Society of Plastics Engineers.