Emulsion atom transfer radical block copolymerization of 2-ethylhexyl methacrylate and methyl methacrylate

The emulsion atom transfer radical block copolymerization of 2-ethylhexyl methacrylate (EHMA) and methyl methacrylate (MMA) was carried out with the bifunctional initiator 1,4-butylene glycol di(2-bromoisobutyrate). The system was mediated by copper bromide/4,4'-dinonyl-2,2'-bipyridyI and stabilized by polyoxyethylene sorbitan monooleate. The effects of the initiator concentration and temperature profile on the polymerization kinetics and latex stability were systematically examined. Both EHMA homopolymerization and successive copolymerization with MMA proceeded in a living manner and gave good control over the polymer molecular weights. The polymer molecular weights increased linearly with the monomer conversion with polydispersities lower than 1.2. A low-temperature prepolymerization step was found to be helpful in stabilizing the latex systems, whereas further polymerization at an elevated temperature ensured high conversion rates. The EHMA polymers were effective as macroinitiators for initiating the block polymerization of MMA. Triblock poly(methyl methacrylate-2-ethylhexyl methacrylate-methyl methacrylate) samples with various block lengths were synthesized. The MMA and EHMA reactivity ratios determined by a non-linear least-square method were similar to 0.903 and similar to 0.930, respectively, at 70 degrees C. (c) 2006 Wiley Periodicals, Inc.