期刊
GREEN CHEMISTRY
卷 21, 期 9, 页码 2469-2477出版社
ROYAL SOC CHEMISTRY
DOI: 10.1039/c9gc00432g
关键词
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资金
- National Natural Science Foundation of China [51673131]
- Special-funded Program on National Key Scientific Instruments and Equipment Development of China [2012YQ230043]
- Fundamental Research Funds for the Central Universities [171gjc37]
We disclose an economical and metal-free catalyst system of (thio)ureas/organic bases for effective fully alternating copolymerization of epoxides and anhydrides, which remains a challenge in sustainable polyester synthesis. A series of commercial (thio) ureas and organic bases were employed as dual catalysts to optimize the activity, and the results indicate that the (thio) ureas with higher basicity paired with quaternary onium salts show higher activity. Particularly, the U1/PPNCl pair shows extremely high TOF (456 h(-1)) toward the ring-opening alternating copolymerization of cyclohexane oxide with phthalic anhydride, which is comparable to the activity of metal-based complex catalysts. Structurally diverse polyesters with high ester linkages (99%) and various glass transition temperatures (ranging from -8 to 133 degrees C) can be obtained by coupling of various renewable epoxides and anhydrides. What's more, structural analysis of the resultant polymers and the interactions between the monomers and the dual catalysts confirmed by H-1 NMR reveal that the (thio)urea can act as a bifunctional catalyst, which activates both the initiating chain end and the monomer through H-bonding in the (thio)urea/PPNCl catalyst system, resulting in high activity.
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