| Synthesis of CO2-based polymeric materials can not only replace nonrenewable crude oil resources but also reduce environment pollution which caused by excessive release of CO2. Although so much progress has been made, synthesis of CO2-based polyurethanes still needs more improvement.Firstly, the copolymerization of2-methyl aziridine and carbon dioxide catalyzed by ionic liquids under supercritical conditions provided a series of aliphatic poly(urethane-amine)s.2-Methyl aziridine was prepared via Wenker synthesis. The results of copolymerization catalyzed by imidazolium-based ionic liquids were better than pyridinium-based ionic liquids, due to the hydrogen bonding donating ability of cations, i.e.[BMim]>[BPy]. The catalytic activity of imidazolium-based ionic liquids was fixed by the cooperative effects of anion-cation, which mostly followed the order of the hydrogen bonding accepting ability and nucleophilicity of anions, or the length of alkyl chains and the amount of substituents of cations. Thus poly(urethane-amine)s with higher urethane contents and molecular weights were obtained, which got various lower critical solution temperatures (LCST) and thermal decomposition temperatures (TDT). The LCST of the poly(urethane-amine) which catalyzed by [BMMim]Cl decreased to35℃, while the poly(urethane-amine) which catalyzed by [BMMim]Cl-DMF had a highest TDT,205.1℃.Besides, the copolymerization of2-methyl aziridine and carbon dioxide catalyzed by IMes (1,3-Bis(2,4,6-trimethylphenyl)imidazol-2-ylidene) was also studied. Using IMes as the catalyst can improve yield and urethane content of the copolymer, but molecular weight remain unchanged. The best reaction condition of which was further discussed:100℃,10MPa,24h as a result.The structures of copolymers were characterized by1H NMR, FT-IR. Element analyzer was used to calculate the urethane contents. The molecular weights of products were determined by MALLS. Thermal decomposition temperatures were characterized by TG. |
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