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Squaramide and amine binary H-bond organocatalysis in polymerizations of cyclic carbonates, lactones, and lactides

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Abstract

Multiple combinations of six squaramides (Sq) and eight amines as the co-catalysts were tried in ring-opening polymerizations (ROPs) of cyclic carbonates, lactones, and lactides. Sq and sparteine co-catalysts enabled ROPs of trimethylene carbonate (TMC) to poly(trimethylene carbonates) (PTMCs) with benzyl alcohol (BnOH) as the initiator. The polymerization proceeded in 3 to 16 h without decarboxylation to afford polycarbonates with precise molecular weights (Mn,NMR = 1.95 to 10.1 kg mol−1) and narrow polydispersity indices (Đ = 1.12–1.17). 1H NMR, SEC and MALDI-ToF MS measurements of the obtained PTMCs clearly indicated the quantitative incorporation of the initiator at the chain end. Kinetics and chain extension experiments demonstrated the controlled/living nature for the ROP of TMC using Sq and sparteine. NMR titration experiments confirmed that the polymerization proceeded in a H-bonding dual activation mechanism. In addition, 1,3-propanediol, pentaerythritol, propargyl alcohol, furfuryl alcohol and N-(2-hydroxyethyl)maleimide were used as functional initiators leading to production of α,ω-dihydroxy telechelic, star-shaped, and clickable end-functionalized polycarbonates. Homopolymers of valerolactone (VL), caprolactone (CL), and lactide (LA) and diblock copolymers PVL-b-PTMC and PCL-b-PTMC were successfully synthesized by using Sq and 1,8-diazabicyclo[5.4.0]undec-7-ene binary co-catalysts with BnOH as the initiator in dichloromethane at room temperature. Block copolymers PTMC-b-PVL, PTMC-b-PCL, and PTMC-b-PLA were successfully obtained by using the binary catalysts. Squaramides combined with amine co-catalysts are a generally applicable polymerization tool.

Graphical abstract: Squaramide and amine binary H-bond organocatalysis in polymerizations of cyclic carbonates, lactones, and lactides

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Publication details

The article was received on 30 Sep 2017, accepted on 31 Oct 2017 and first published on 31 Oct 2017


Article type: Paper
DOI: 10.1039/C7PY01671A
Citation: Polym. Chem., 2017, Advance Article
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    Squaramide and amine binary H-bond organocatalysis in polymerizations of cyclic carbonates, lactones, and lactides

    J. Liu, J. Xu, Z. Li, S. Xu, X. Wang, H. Wang, T. Guo, Y. Gao, L. Zhang and K. Guo, Polym. Chem., 2017, Advance Article , DOI: 10.1039/C7PY01671A

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