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<p>Zwitterionic ring-opening polymerization (ZROP) is widely used synthetic methods for cyclic polymer synthesis. While various ZROP studies utilizing organic base catalysts have been explored, reports involving 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) are rare, leaving the specific ZROP mechanism unclear. In this study, we investigate the polymerization mechanism using TBD and trimethylene carbonate (TMC). Polymerization kinetics studies reveal an irreversible formation of initiation species at the initiation reaction, showing deviation from known ZROP mechanisms using <i>N</i>-heterocyclic carbene as organic base catalysts. Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF–MS) results indicate that polymerization attempts using polar solvents like THF stabilize active zwitterionic species and prevent side reactions. Based on our kinetics study, we quantitatively demonstrate that TBD-catalyzed ZROP of TMC proceeds via an effectively irreversible initiation step, exhibiting first-order dependence on TBD concentration. Furthermore, detailed MALDI-TOF–MS analysis, including minor polymer populations (L2 and L3), reveals solvent-dependent suppression of intermolecular exchange reactions. These findings provide mechanistic insights beyond previous reports and clarify the distinct behavior of TBD in ZROP of TMC.</p> Graphical abstract <p>We investigated the polymerization mechanism of trimethylene carbonate monomer using TBD in the absence of alcohol. Our findings revealed that despite the polymerization progressing via ZROP, the initiation reaction is irreversible. We hypothesize that the deprotonation of TBD leads to the dissolution of zwitterion, resulting in the formation of a mixture of cyclic and linear polymers.</p> <p></p>

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Kinetic and mechanistic investigation of the zwitterionic ring-opening polymerization of trimethylene carbonate catalyzed by 1,5,7-triazabicyclo[4.4.0]dec-5-ene

  • 期刊论文

  • 发表日期：

    2026年5月18日

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  • Naoto Hirano,
  • Hiroaki Yoshida,
  • Hiroharu Ajiro

摘要

Zwitterionic ring-opening polymerization (ZROP) is widely used synthetic methods for cyclic polymer synthesis. While various ZROP studies utilizing organic base catalysts have been explored, reports involving 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) are rare, leaving the specific ZROP mechanism unclear. In this study, we investigate the polymerization mechanism using TBD and trimethylene carbonate (TMC). Polymerization kinetics studies reveal an irreversible formation of initiation species at the initiation reaction, showing deviation from known ZROP mechanisms using N-heterocyclic carbene as organic base catalysts. Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF–MS) results indicate that polymerization attempts using polar solvents like THF stabilize active zwitterionic species and prevent side reactions. Based on our kinetics study, we quantitatively demonstrate that TBD-catalyzed ZROP of TMC proceeds via an effectively irreversible initiation step, exhibiting first-order dependence on TBD concentration. Furthermore, detailed MALDI-TOF–MS analysis, including minor polymer populations (L2 and L3), reveals solvent-dependent suppression of intermolecular exchange reactions. These findings provide mechanistic insights beyond previous reports and clarify the distinct behavior of TBD in ZROP of TMC.

Graphical abstract

We investigated the polymerization mechanism of trimethylene carbonate monomer using TBD in the absence of alcohol. Our findings revealed that despite the polymerization progressing via ZROP, the initiation reaction is irreversible. We hypothesize that the deprotonation of TBD leads to the dissolution of zwitterion, resulting in the formation of a mixture of cyclic and linear polymers.