Comparison of RAFT Ab Initio Emulsion Polymerization of Methyl Methacrylate and Styrene Mediated by Oligo(methacrylic acid-b-methyl methacrylate) Trithiocarbonate Surfactant

The comparison between methyl methacrylate (MMA) and styrene (St) RAFT emulsion polymerization using oligo(methacrylic acid41-b-methyl methacrylate(8)) RAFT agent (oligo(MAA(41)-b-MMA(8)) RAFT) as surfactant is investigated in order to gain a better understanding on RAFT emulsion polymerization of MMA. It is found that the colloidal stability during MMA emulsion polymerization is much more sensitive to the initiator concentrations and temperature than that of St polymerization. The coagulum-free latex of highly living PMMA can be achieved only at 80 degrees C and low initiator concentrations. The final PDI is higher in RAFT emulsion polymerization of MMA than that of St. It is revealed that about 40% acid groups of oligo(MAA(41)-b-MMA(8)) RAFT should be buried within the final particles of PMMA, indicating that particle coagulation should occur in the very beginning of the polymerization. The poorer performance of the MMA polymerization could be well explained by the homogeneous nucleation mode of particles combined with relatively slow transporting rate of oligo(MAA41-b-MMA(8)) RAFT molecules from the partly frozen micelles to the newly-born particles.