The RAFT-mediated, surfactant-free, ab initio, batch emulsion polymerization of n-butyl acrylate (nBA) and its copolymerization with methyl methacrylate (MMA) were studied. The control agent was a surface-active trithiocarbonate macromolecular RAFT agent composed of a hydrophilic poly(ethylene oxide) (PEO) block and a hydrophobic dodecyl chain. The homopolymerizations of nBA were fast with high Final conversions, and the polymer chains were well-controlled with narrow molar mass distribution. The length of the PEO chain was shown to affect the particle size and the polymerization kinetics directly. We found the conditions to time the particle size independently from the poly(n-butyl acrylate) chain length by playing with a mixture of macro-RAFT agents with long and short PEO segment or by adding a PEO-based nonionic surfactant. The copolymerizations of nBA and MMA exhibited features very similar to those of the nBA homopolymerizations provided that the molar percentage of M MA did not exceed approximately 75%. In all cases, stable, submicrometric particles composed of amphiphilic diblock copolymer chains were formed.