期刊
MACROMOLECULES
卷 49, 期 3, 页码 807-814出版社
AMER CHEMICAL SOC
DOI: 10.1021/acs.macromol.5b02752
关键词
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资金
- National Science Foundation [CHE-1057743]
- Robert A. Welch Foundation [A-0923]
- Hundred Talents Program of Zhejiang University from China
The addition of water as a chain transfer reagent during the copolymerization reaction of epoxides and cabondioxide has been shown as a promising method for producing CO2-based polycarbonate polyols. These polyols can serve drop-in replacements for petroleum derived polyols for polyurethane production or designer block copolymers. Ironically, during the history of CO2/epoxide coupling development, water was generally considered primarily as an aversion reagent. That is, in its presence, low catalytic activity and high polydispersity was normally observed. Recently, we reported a water-mediated tandem metal-coordination CO2/epoxide copolymerization and organobase catalyzed ring-opening polymerization (ROP) approach for the one-pot synthesis of an ABA CO2-based triblock copolymers. As in previous studies, water was deemed as the chain transfer reagent in this tandem strategy for producing CO2-based polyols. Herein is presented a mechanistic study aimed at determining the intimate role water plays during the metal-catalyzed CO2/epoxide copolymerization process. In this regard, it was observed that under the commonly employed (salen)Co(trifluoroacetate)/onium salt binary catalyst system, water was not the true chain-transfer reagent, but instead reacted initially with the epoxides to afford the corresponding diols which serves as the chain-transfer reagent. The further studies in resultant afforded alpha,omega-dihydroxyl end capped polycarbonates were utilized in direct chain extension via ROP of the water-soluble cyclic phosphate monomer, 2-methoxy-2-oxo-1,3,2-dioxaphospholene employing an organocatalyst. These triblock copolymers displayed narrow PDI and were found to provide nanostructure materials which should be of use in biomedical applications.
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