RAFT-mediated controlled free-radical polymerization has been developed in an oil surfactant-free dispersed system: this system involves the dispersion polymerization of methyl acrylate in isododecane using soluble macromolecular RAFT agents (poly(2-ethylhexyl acrylate)) based either on a dithiobenzoate reactive group or on a trithiocarbonate one. The conditions to find a good control over the polymer chain growth together with formation of well-defined, self-stabilized particles have been examined. The process takes advantage of the in situ formation of amphiphilic block copolymers that self-assemble simultaneously with the growth step to form block copolymer micelles. The reactions are performed in very simple conditions, at high concentration and with a limited number of reactants. The comparison of the two systems, together with a detailed 2D chromatography characterization of the block copolymers enabled us to propose a mechanism. It appears that the quality of control over both the macromolecular structure and the colloidal characteristics strongly depends on the reactivity of the macroRAFT agent and its solvophilic/solvophobic character.
