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Issue 26, 2019
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Dynamic covalent urea bonds and their potential for development of self-healing polymer materials

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Abstract

Self-healing polymer materials have drawn rapidly increasing interest over the last decade, and have been studied and used in an ever-increasing range of applications. Herein, we successfully make the covalent urea bond – a pinnacle of stability due to strong resonance effects – dynamic in nature through mediation of zinc salts. The dynamic covalent character of urea in the presence of zinc ions is confirmed through dissociation reaction experiments and quantum chemical calculations of small-molecule model urea compounds. In line with our experiments, the modelling results suggest that the presence of zinc ions speeds up the reaction of urea dissociation by two orders of magnitude via the formation of O-bound Zn complexes. Based on such dynamic covalent urea bonds, we then develop a novel class of self-healing polymer materials with excellent healing efficiencies. Different kinds of self-healing and reprocessable polyurea materials were prepared, with polymer properties that can be easily tuned by varying the degree of crosslinking and the molecular weight of the siloxane precursor. Since different kinds of self-healing polyurea materials could easily be prepared due to the commercial availability of a very wide range of amine and isocyanate monomers, this introduction of self-healing properties is expected to have significant potential in a range of applications, such as coatings, paints, and 3D printing. In addition, this introduces polyureas and other urea-containing polymers as a class of highly stable, yet easily reprocessable plastics, which is highly relevant given the globally desired more sustainable use of plastics.

Graphical abstract: Dynamic covalent urea bonds and their potential for development of self-healing polymer materials

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Publication details

The article was received on 23 Feb 2019, accepted on 19 May 2019 and first published on 18 Jun 2019


Article type: Paper
DOI: 10.1039/C9TA02054C
J. Mater. Chem. A, 2019,7, 15933-15943
  • Open access: Creative Commons BY-NC license
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    Dynamic covalent urea bonds and their potential for development of self-healing polymer materials

    Z. Wang, S. Gangarapu, J. Escorihuela, G. Fei, H. Zuilhof and H. Xia, J. Mater. Chem. A, 2019, 7, 15933
    DOI: 10.1039/C9TA02054C

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