Synthesis by RAFT of amphiphilic block and comblike cationic copolymers and their use in emulsion polymerization for the electrosteric stabilization of latexes
Résumé
A series of diblock and comblike copolymers based on styrene and 4-vinylbenzyl chloride were synthesized by reversible addition fragmentation transfer (RAFT) using benzyl dithiobenzoate as a control agent. After quaternization of the well-defined hydrophobia precursors with triethylamine, the micellar aggregates, formed by the cationic amphiphilic diblock copolymer when dissolved in water, were investigated by static and dynamic light scattering. The spherical shape of the micelles was established in salted water. Then, the poly(styrene)-b-poly(vinylbenzyltriethylammonium chloride) cationic diblock copolymers were used as a stabilizer for the emulsion polymerization of styrene and appeared to display very good stabilization properties. The ratio between the initial number of micelles and the final number of latex particles was particularly high, as a characteristic of the high mobility of the copolymer chains. Finally, we underlined the strong influence of salt on the nucleation step of the emulsion polymerization. The influence of the architecture of the copolymers on the stabilization of latexes has also been established by using random copolymers quaternized with N,N-dimethyldodecylamine, which led to cationic comblike copolymers. They were used for the first time as stabilizers for the emulsion polymerization of styrene. These amphiphilic copolymers proved to be good stabilizers in very low proportions (0.5-1 wt% styrene), which makes them valuable due to their simple synthesis.