Thermal and pH Responsive High Molecular Weight Poly(urethane-amine) with High Urethane Content

Aliphatic poly(urethane-amine) (PUA) was synthesized from copolymerization of CO(2) and 2-methylaziridine (MAZ) using Y(CC(l)3COO)(3)-ZnEt(2)-glycerine coordination catalyst, the urethane content of PUA was over 80%, and its yield could reach 90%. PUA with molecular weight as high as 31.0 kg/mol was obtained when the copolymerization reaction was carried out in N,N-dimethylacetamide (DMAc), mainly due to the good solubility of PUA in DMAc. PUA exhibited reversible thermo-responsive property in deionized water, and the lower critical solution temperature (LCST) was highly sensitive to its urethane content and molecular weight, which was observed in a broad window from 37 to 90 degrees C. Furthermore, the phase transition behavior could also be controlled by change of pH value. When the pH value of the PUA aqueous solution changed from 9.2 to 13, the LCST value of the solution decreased from 48.4 degrees C to 30 degrees C. Therefore, the PUA showed thermo-and pH-dual responsive performance in water. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 5162-5168, 2011