Lower Critical Solution Temperature Behavior of Comb and Graft Shaped Poly[oligo(2-ethyl-2-oxazoline)methacrylate]s

Comb and graft polymers with lower critical solution temperature (LCST) behavior based on hydrophilic oligo(2-ethyl-2-oxazoline) side chains and a hydrophobic methacrylate backbone were synthesized using the macromonorner method. Well-defined oligo(2-ethyl-2-oxazoline) methacrylate (OEtOxMA) macromonomers were obtained by direct end-capping of living oligo(2-ethyl-2-oxazoline) chains with in situ formed triethylammonium methacrylate. The macromonomers were subsequently polymerized in a controlled manner using the reversible addition - fragmentation chain transfer (RAFT) polymerization technique yielding a series of comb polymers with varying side chain length and backbone length. In addition, a series of graft copolymers were prepared by copolymerizing OEtOxMA with methyl methacrylate (MMA, 40-80 mol%). The copolymers were characterized by H-1 NMR spectroscopy, size exclusion chromatography (SEC), and, partially, by matrix-assisted laser desorption ionization (MALDI-TOF) mass spectrometry. The LCST behavior of aqueous polymer solutions was investigated by turbidity measurements revealing cloud points that can be tuned from 35 to 80 degrees C by variation of the NIMA content.