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<p>Based on the study of thiol-epoxy click chemistry under bulk polymerization conditions, this study addresses the challenge of uncontrollably fast curing kinetics in traditional systems by establishing a pKa-based mechanism-reactivity relationship and proposing a proton-mediated on-demand curing strategy. Through systematic investigation using catalysts with varying acid dissociation constants (pKa), we clarify that the reaction proceeds via a base-catalyzed mechanism when the catalyst’s pKa significantly exceeds that of the thiol, whereas a nucleophilic addition-initiated mechanism dominates when the catalyst’s pKa is lower. Building on this mechanistic insight, the introduction of a proton donor (mercaptopropionic acid, MPA) enables precise regulation of the reaction kinetics. By constructing a “proton donor–catalyst–thiol” triad with a sequential pKa gradient (pKa of proton donor &lt; pKa of catalyst &lt; pKa of thiol), a prolonged and stable dormant period is achieved, after which rapid, autocatalytic polymerization proceeds. This approach successfully decouples pot life from curing speed, transforming the epoxy-thiol system from “immediately reactive” to “curable on-demand.” Furthermore, the effects of epoxy electrophilicity and thiol pKa on the kinetics are elucidated. This study not only resolves long-standing mechanistic controversies but also provides a universal, predictable, and easily implementable chemical framework for designing advanced thermosetting materials with tailored processability and performance.</p>

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Controlling thiol-epoxy click chemistry: A unified framework via catalyst pKa and proton management for on-demand curing

  • 期刊论文

  • 发表日期：

    2026年5月26日

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  • Zhipeng Ran,
  • Yeping Wu,
  • Mao Chen,
  • Yinyu Zhang,
  • Peishuang Xiao,
  • Keping Chen,
  • Xiuli Zhao

摘要

Based on the study of thiol-epoxy click chemistry under bulk polymerization conditions, this study addresses the challenge of uncontrollably fast curing kinetics in traditional systems by establishing a pKa-based mechanism-reactivity relationship and proposing a proton-mediated on-demand curing strategy. Through systematic investigation using catalysts with varying acid dissociation constants (pKa), we clarify that the reaction proceeds via a base-catalyzed mechanism when the catalyst’s pKa significantly exceeds that of the thiol, whereas a nucleophilic addition-initiated mechanism dominates when the catalyst’s pKa is lower. Building on this mechanistic insight, the introduction of a proton donor (mercaptopropionic acid, MPA) enables precise regulation of the reaction kinetics. By constructing a “proton donor–catalyst–thiol” triad with a sequential pKa gradient (pKa of proton donor < pKa of catalyst < pKa of thiol), a prolonged and stable dormant period is achieved, after which rapid, autocatalytic polymerization proceeds. This approach successfully decouples pot life from curing speed, transforming the epoxy-thiol system from “immediately reactive” to “curable on-demand.” Furthermore, the effects of epoxy electrophilicity and thiol pKa on the kinetics are elucidated. This study not only resolves long-standing mechanistic controversies but also provides a universal, predictable, and easily implementable chemical framework for designing advanced thermosetting materials with tailored processability and performance.