The “coordination-insertion” ring-opening polymerization (ROP) mechanism has so far been the monopoly of metal catalysts. In this work, we present a metal-free “coordination-insertion” ROP of trimethylene carbonate (TMC) and ε-caprolactone (ε-CL), as well as their sequential block copolymerization, with N-trimethylsilyl-bis (trifluoromethanesulfonyl)imide (TMSNTf2) as the non-metallic initiator/catalyst. TMSNTf2 was proposed to work through an unprecedented metal-free “coordination-insertion” mechanism, which involves the coordination of monomer to the Si atom of TMSNTf2, the nucleophilic attack of the –NTf2 group on the coordinated monomer, and the cleavage of the acyl–oxygen bond of the monomer. The proposed metal-free “coordination-insertion” ROP was studied by NMR, SEC, and MALDI-TOF analyses. In addition, the TMSNTf2-mediated ROP of TMC and ε-CL led to linear and cyclic polymers following two-stage first-order polymerization processes, as evidenced by structural analyses and kinetics study, which further demonstrated the metal-free “coordination-insertion” mechanism.
Bibliographical noteKAUST Repository Item: Exported on 2021-06-21
Acknowledgements: This work was supported by the National Natural Science Foundation of China (22078150), the National Key Research and Development Program of China (2017YFC1104802), the Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), the project funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD), and the Top-Notch Academic Programs Project of Jiangsu Higher Education Institutions (TAPP). N. H. acknowledges the support of King Abdullah University of Science and Technology.
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