RAFT Dispersion\nPISA with Poly(methyl methacrylate)\nas Stabilizer Block in Alcohol/Water: Unconventional PISA Morphology\nTransitions

Reversible\naddition–fragmentation chain transfer\n(RAFT)\ndispersion polymerization-induced self-assembly (PISA) was conducted\nin the presence of poly(methyl methacrylate) (PMMA) stabilizer in\nethanol/water mixture (80/20 by volume). Two different systems were\nexplored by utilizing (i) 2-ethylhexyl methacrylate (EHMA) and (ii) <i>n</i>-butyl methacrylate (BMA). The morphology transitions of\nthese systems were investigated by varying the polymerization conditions,\ni.e., the presence of the solvophilic comonomer MMA, the solids content,\nand the target degree of polymerization (DP). As observed in conventional\nPISA, the presence of solvophilic comonomer, increase in solids content\nand target DP promoted the formation of high-order morphology. However,\nunusual morphology transitions were observed whereby the morphology\ntransformed from high-order morphologies to a mixture of spherical\nnanoparticles, worms, and vesicles and finally to vesicles with increasing\ntarget DP. This unusual evolution may be attributed to the limited\nsolubility of PMMA in the ethanol/water solvent mixture, whereby PMMA\nis soluble at the polymerization temperature but insoluble at lower\ntemperatures.