Laser light scattering study of microemulsion-like polymerization processes with block copolymers as dispersants

Laser light scattering (LLS) was employed to monitor the microemulsion-like polymerization processes by using poly(methyl methacrylate)-b-poly(methacrylic acid) (P(MMA-b-MAA)) block copolymers with different block lengths (MMA(58)-b-MAA(57), MMA(67)-b-MAA(217), and MMA(32)-b-MAA(69)) or sodium dodecyl sulfate (SDS) surfactant as dispersants. A combination of static and dynamic light scattering techniques (SLS and DLS) was used to monitor the microemulsion-like systems before, during, and after polymerization. The polymerization of MMA (methyl methacrylate) was found to occur first in the dispersing aqueous medium, and then it was transferred inside the micellar cores to continue the polymerization process, which is similar to the homogeneous nucleation mechanism found when using small-molecule surfactants as dispersants. Depending on the hydrophobicity of the micellar cores, a rearrangement of micellar chains was found to take place during the different stages of the polymerization process. The similarities and differences of the dispersants between SDS surfactant micelles and P(MMA-b-MAA) block copolymer micelles are discussed. The polymerization of n-BA in micellar solution was also studied and compared with that of MMA.