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<p>Nonisocyanate polyurethanes (NIPUs) offer a safer and more sustainable alternative to conventional polyurethanes, which rely on toxic isocyanates. In this study, a high molecular weight (&gt; 40,000&#xa0;g/mol) self-healing NIPU was synthesized via a two-step copolymerization process. Initially, ethylene carbonate reacted with 4,4′-methylene dianiline (4,4′-MDA) to form a hydroxyl-terminated urethane monomer (hydroxyurethane, HU). This intermediate was subsequently copolymerized with polycaprolactone diol (PCL-diol), adipic acid (ADA), and 3,3′-dithiodipropionic acid (DTDPA) to yield a hybrid polyhydroxyurethane containing reversible disulfide bonds. The successful synthesis of the HU monomer and the resulting NIPU products was confirmed via FTIR, NMR, LC–MS, and Raman spectroscopy. GPC analysis demonstrated that molecular weight and dispersity increased with HU content, with NIPU-6 exhibiting the highest M<sub>n</sub> (4.9 × 10<sup>4+</sup>&#xa0;g/mol). DSC analysis revealed that higher HU content disrupted crystallinity, while mechanical testing showed a corresponding increase in elongation at break (from 29 to 243%) but a decrease in yield stress and Young’s modulus. Self-healing efficiency, assessed via tensile testing, improved with both HU and DTDPA contents. NIPU-6 (HU: PCL-diol: DTDPA: ADA = 15:35:37.5:12.5&#xa0;mol.%) had the highest M<sub>n</sub> (4.9 × 10<sup>4+</sup>&#xa0;g/mol) and exhibited the highest self-healing performance, achieving 98.5% recovery in tensile strength and 97.8% in elongation at break after thermal healing at 50&#xa0;°C. These findings highlight the potential of NIPUs with dynamic disulfide bonds as durable, repairable, and environmentally friendly materials for applications in coatings and flexible electronics.</p> Graphical abstract <p></p>

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Synthesis and characterization of high molecular weight self-healing nonisocyanate polyurethanes with dynamic disulfide linkages

  • 期刊论文

  • 发表日期：

    2025年12月1日

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  • Reza Rezaie,
  • Gity Mir Mohamad Sadeghi,
  • Seyed Morteza Ghasemi

摘要

Nonisocyanate polyurethanes (NIPUs) offer a safer and more sustainable alternative to conventional polyurethanes, which rely on toxic isocyanates. In this study, a high molecular weight (> 40,000 g/mol) self-healing NIPU was synthesized via a two-step copolymerization process. Initially, ethylene carbonate reacted with 4,4′-methylene dianiline (4,4′-MDA) to form a hydroxyl-terminated urethane monomer (hydroxyurethane, HU). This intermediate was subsequently copolymerized with polycaprolactone diol (PCL-diol), adipic acid (ADA), and 3,3′-dithiodipropionic acid (DTDPA) to yield a hybrid polyhydroxyurethane containing reversible disulfide bonds. The successful synthesis of the HU monomer and the resulting NIPU products was confirmed via FTIR, NMR, LC–MS, and Raman spectroscopy. GPC analysis demonstrated that molecular weight and dispersity increased with HU content, with NIPU-6 exhibiting the highest Mn (4.9 × 104+ g/mol). DSC analysis revealed that higher HU content disrupted crystallinity, while mechanical testing showed a corresponding increase in elongation at break (from 29 to 243%) but a decrease in yield stress and Young’s modulus. Self-healing efficiency, assessed via tensile testing, improved with both HU and DTDPA contents. NIPU-6 (HU: PCL-diol: DTDPA: ADA = 15:35:37.5:12.5 mol.%) had the highest Mn (4.9 × 104+ g/mol) and exhibited the highest self-healing performance, achieving 98.5% recovery in tensile strength and 97.8% in elongation at break after thermal healing at 50 °C. These findings highlight the potential of NIPUs with dynamic disulfide bonds as durable, repairable, and environmentally friendly materials for applications in coatings and flexible electronics.

Graphical abstract