This study was focused on the synthesis of monodisperse poly(n-butyl methacrylate-co-methyl methacrylate) submicrospheres via soap-free emulsion polymerization and on their characterization. The glass-transition temperatures of poly(n-butyl methacrylate) and poly(methyl methacrylate) were approximately 25 and 110 degrees C, respectively. Therefore, submicrospheres with different glass-transition temperatures could be obtained through the variation of the copolymer composition. In addition, relationships between the monomer feed concentration (M(0)) and the Mark-Houwink constant (alpha) for the copolymer submicrospheres were proposed. The molecular weights of the copolymer submicrospheres decreased sharply with an increase in the weight fraction of n-butyl methacrylate. On the contrary, the particle diameter increased linearly from 277 to 335 nm with an increase in the weight fraction of n-butyl methacrylate. The a values decreased with an increase in M(0), and this indicated that the branched structures of the copolymer submicrospheres were easily obtained when M(0) was higher than 0.11 g/mL of water. Consequently, the results of this study are expected to provide useful information for the synthesis of monodisperse copolymer submicrospheres by soap-free emulsion polymerization. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 120: 2945-2953, 2011