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Abstract <p>This study reveals the kinetic mechanisms behind piperylene’s activating role in the GdCl<sub>3</sub>·<i>n</i>(<i>i</i>-C<sub>3</sub>H<sub>7</sub>OH)–TIBA–piperylene catalytic system for isoprene polymerization. Piperylene addition (1) forms three types of active centers (ACs), including two novel piperylene-derived ACs with initiation rate constants <i>kᵢ</i> ≥ 10 M<sup>–1</sup> min<sup>–1</sup> enabling quasi-instantaneous polymerization onset; (2) increases total precatalytic center concentration 18-fold (9 × 10<sup>–6</sup> M vs. 5 × 10<sup>–7</sup> M without piperylene); and (3) induces AC deactivation: Type 1 ACs (<i>k</i><sub><i>p</i></sub> = 40 000 M<sup>–1</sup> min<sup>–1</sup>, <i>k</i><sub><i>d</i></sub> = 10 min<sup>–1</sup>) produce short chains and deactivate rapidly, while Type 2 ACs (<i>k</i><sub><i>p</i></sub> = 86 000 M<sup>–1</sup> min<sup>–1</sup>, <i>k</i><sub><i>d</i></sub> = 0.1 min<sup>–1</sup>) remain active for ≤30 min. Notably, high-MW Type 3 ACs (<i>k</i><sub><i>p</i></sub> = 146 000 M<sup>–1</sup> min<sup>–1</sup>) persist, mirroring non-piperylene systems. Kinetic modeling (including Monte Carlo simulations) validated the deactivation-inclusive Scheme II, accurately describing monomer conversion, MWDs and molecular weights. These results elucidate piperylene’s acceleration effect and may extend to other Ziegler–Natta diene-polymerization systems.</p>

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On Kinetic Reasons for the Activating Effect of Piperylene in Isoprene Polymerization on the Catalyst System GdCl3⋅n(i-C3H7ОН)–TIBA–Piperylene

  • 期刊论文

  • 发表日期：

    2025年8月1日

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  • S. V. Kolesov,
  • N. V. Plotnikova,
  • D. V. Stiazhkin,
  • V. M. Yanborisov

摘要

Abstract

This study reveals the kinetic mechanisms behind piperylene’s activating role in the GdCl3·n(i-C3H7OH)–TIBA–piperylene catalytic system for isoprene polymerization. Piperylene addition (1) forms three types of active centers (ACs), including two novel piperylene-derived ACs with initiation rate constants kᵢ ≥ 10 M–1 min–1 enabling quasi-instantaneous polymerization onset; (2) increases total precatalytic center concentration 18-fold (9 × 10–6 M vs. 5 × 10–7 M without piperylene); and (3) induces AC deactivation: Type 1 ACs (kp = 40 000 M–1 min–1, kd = 10 min–1) produce short chains and deactivate rapidly, while Type 2 ACs (kp = 86 000 M–1 min–1, kd = 0.1 min–1) remain active for ≤30 min. Notably, high-MW Type 3 ACs (kp = 146 000 M–1 min–1) persist, mirroring non-piperylene systems. Kinetic modeling (including Monte Carlo simulations) validated the deactivation-inclusive Scheme II, accurately describing monomer conversion, MWDs and molecular weights. These results elucidate piperylene’s acceleration effect and may extend to other Ziegler–Natta diene-polymerization systems.