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).

Reversible addition-fragmentation chain transfer (RAFT) polymerizations have been performed on a Chemspeed Accelerator SLT100 automated synthesizer to polymerize N,N-(dimethylamino)ethyl methacrylate (DMAEMA) and poly(ethylene glycol) methyl ether methacrylate (PEGMA) at 70 °C. Azobis(isobutyronitrile) (AIBN) was used as source of radicals and 2-cyano-2-butyl dithiobenzoate (CBDB) as RAFT agent. A complete screening in composition of P(DMAEMA-stat-PEGMA) copolymers was elaborated from 0% of PEGMA to 100% of PEGMA. All polydispersity indices of the obtained copolymers are comprised between 1.11 and 1.30. The reactivity ratios have been determined by the extended Kelen-Tu ¨do ¨s method (r DMAEMA ) 0.93 and r PEGMA ) 0.66). The behavior of the pH-and temperature-sensitive copolymers was studied in aqueous solution by measuring the lower critical solution temperature (LCST) by UV/vis spectroscopy. The measurements were performed at three different pH values (4, 7, and 10). At pH 7 and pH 10 it has been observed that the LCST is increasing linearly with the wt % PEGMA in the copolymer feed. On the contrary, at pH 4, the hydrophilicity of the P(DMAEMA-stat-PEGMA) copolymers is too high due to the protonation of the DMAEMA units. Thus, no LCST has been detected for most of them. By varying the pH and the composition of the P(DMAEMA-stat-PEGMA) copolymers, the LCST can be easily tuned between 34.7 and 82.0 °C.

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