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(methacr ylic acid) (P(MMA-b-MAA)) block copolymers with different block lengths (MM A(58)-b-MAA(57), MMA(67)-b-MAA(217), and MMA(32)-b-MAA(69)) or sodium dodec yl sulfate (SDS) surfactant as dispersants. A combination of static and dyn amic light scattering techniques (SLS and DLS) was used to monitor the micr oemulsion-like systems before, during, and after polymerization. The polyme rization of MMA (methyl methacrylate) was found to occur first in the dispe rsing aqueous medium, and then it was transferred inside the micellar cores to continue the polymerization process, which is similar to the homogeneou s nucleation mechanism found when using small-molecule surfactants as dispe rsants. Depending on the hydrophobicity of the micellar cores, a rearrangem ent of micellar chains was found to take place during the different stages of the polymerization process. The similarities and differences of the disp ersants between SDS surfactant micelles and P(MMA-b-MAA) block copolymer mi celles are discussed. The polymerization of n-BA in micellar solution was a lso studied and compared with that of MMA.