The cloud point of copolymers of 2-ethyl-2-oxazoline and 2-n-propyl-2-oxazoline could be tuned from 25 degrees C to 100 degrees C by varying molecular weight and composition; the reversibility and concentration dependence of the cloud points were evaluated to assess the potential of these copoly(2-oxazoline)s as alternatives to poly(N-isopropylacrylamide).

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 OEGMA 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 C, whereas at a pH value of 7, the CPs were found to be 20.6, 93.7, and 20.0 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 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 C, measured at pH values of 2, 4, and 7, while no cloud point was detected at pH 10. V

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