Libraries of Methacrylic Acid and Oligo(ethylene glycol) Methacrylate Copolymers with LCST Behavior

Homopolymers of methacrylic acid (MAA), monoethyleneglycol methyl ether methacrylate (MEOMA), diethyleneglycol methyl ether methacrylate (MEO(2)MA), oligo(ethyleneglycol) methyl ether methacrylate (OEGMA(475) and CEGMA(1100)) and oligo(ethyleneglycol) ethyl ether methacrylate (OEGEMA(246)) were synthesized with various chain lengths via reversible addition fragmentation chain transfer (RAFT) polymerization. The homopolymers of MAA, MEOMA and OEGMA(1100) did not show any cloud point (CP) in the range of 0-100 degrees C, whereas at a pH value of 7, the CPs were found to be 20.6, 93.7, and 20.0 degrees C for p(MEO(2)MA), p(OEGMA(475)) and p(OEGEMA(246)), respectively, with an initial monomer to initiator ratio of 50. Furthermore, statistical copolymer libraries of MAA with OEGMA(475) and OEGMA(1100) were prepared. The cloud points of the random copolymers of MAA and OEGMA(475) were found to be in the range of 20-90 degrees C; surprisingly, even though the homopolymers of MAA and OEGMA(1100) did not exhibit any LCST behavior, the copolymers of these monomers at certain molar ratios (up to 40% OEGMA(1100)) revealed a double responsive behavior for both temperature and pH. Finally, the cloud points were found to be in the range of 22-98 degrees C, measured at pH values of 2, 4, and 7, while no cloud point was detected at pH 10. (C) 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7138-7147, 2008