158: New perspectives for NIPUs : linear polyhydroxyurethanes of high-molecular weight obtained by fast polymerization.

Conventional methods for synthesizing thermoplastic polyurethanes (TPUs) typically rely on isocyanates and catalysts, both of which present significant environmental and safety risks. To mitigate ecological impact and health hazards, the development of non-isocyanate polyurethanes (NIPUs) is crucial. Polyhydroxyurethanes (PHUs) in particular show great potential due to the low toxicity of the monomers and the relative ease of synthesis, but suffer from slow polymerization kinetics [1, 2, 3] and side reactions that decrease their degree of polymerization (DP_n) and materials properties. In particular, DP_n values for these materials tend to plateau around 30 and rarely exceed 40 [4].

This study reports a new, rapid PHU polymerization from di-functional monomers achieved without macromonomers, catalysts, or post-condensation reactions [5]. Thanks to the unique reactivity of aromatic cyclic carbonates (ACC) with amines – particularly cycloaliphatic secondary amines (CAA) – model systems give 100% conversion within minutes with minimal secondary reactions. This approach has been successfully extended for the first time to the rapid synthesis of linear PHU chains. A range of difunctional ACC and CAA monomers with diverse chemical structures have been utilized to optimize reactivity, minimize side reactions, and achieve high DP_n and molecular weights (M_n). The synthesized PHUs were characterized using nuclear magnetic resonance (NMR), Fourier-transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The highest DP_n and M_n obtained were ~220 and ~105,000 g/mol, respectively. These PHUs were subsequently molded into bars and analyzed via thermo-mechanical techniques, demonstrating significant potential for future applications.

[1] Besse, V.; Camara, F.; Méchin, F.; Fleury, E.; Caillol, S.; Pascault, J.-P.; Boutevin, B. How to Explain Low Molar Masses in PolyHydroxyUrethanes (PHUs). Eur. Polym. J. 2015, 71, 1−11. DOI: 10.1016/j.eurpolymj.2015.07.020.
[2] Blain, M.; Cornille, A.; Boutevin, B.; Auvergne, R.; Benazet, D.; Andrioletti, B.; Caillol, S. Hydrogen Bonds Prevent Obtaining High Molar Mass PHUs. J. Appl. Polym. Sci. 2017, 134 (45), 44958. DOI: 10.1002/app.44958.
[3] Ecochard, Y.; Caillol, S. Hybrid Polyhydroxyurethanes: How to Overcome Limitations and Reach Cutting Edge Properties? Eur. Polym. J. 2020, 137, 109915. DOI: 10.1016/j.eurpolymj.2020.109915.
[4] Benyahya, S.; Boutevin, B.; Caillol, S.; Lapinte, V.; Habas, J.-P. Optimization of the Synthesis of Polyhydroxyurethanes Using Dynamic Rheometry. Polym. Int. 2012, 61 (6), 918−925. DOI: 10.1002/pi.4159.
[5] Zubkevich, S.V.; Shaplov, A.S.; Schmidt D.F. Method for the synthesis of high molecular weight polyhydroxyurethanes. LU509504, 2024.