A fully healable, mechanical self-strengthening and antibacterial Poly(thiocarbamate-urethane) elastomer constructed via dual reversible dynamic networks

Crosslinked polyurethane elastomers may irreversibly suffer from some external damage such as chemical corrosion, stress and long-term heat treatment, inducing the formation of the microcracks and reduction of mechanical performance. Herein, a novel, fully healable and mechanical self-strengthening crosslinked poly(thiocarbamate-urethane) elastomers (PTU) are constructed by dual reversible dynamic networks, which are based on the thiol-isocyanate click reaction and 2, 4-diamino-6-hydroxy-pyrimidine-Zn2+ (HPM-Znx) coordination effect. Interestingly, the tensile strength and toughness of PTU-HPM-Zn1/4 reached 24.2 MPa and 46.3 MJ/m3, which are 3.6 and 1.6 times higher than those of PTU-HPM, due to the coordination effect between Zn2+ and pyrimidine that formed a denser cross-linking network. Interestingly, the snipped specimen of PTU-HPM-Zn1/4 are fully healable within 12 h at 70 °C. Moreover, the hot-reprocessed PTU-HPM-Zn1/4 sample were further increased to 25.0 MPa and 51.5 MJ/m3, showing a mechanical self-strengthening phenomenon. These impressive mechanical properties of PTU-HPM-Zn1/4 elastomer are attributed to the hierarchical structure evolution including the microphase separation between crystallized and amorphous regions, and the multi reversible dynamic networks reconstruction of thiocarbamate, coordination and hydrogen bonds in the system. Meanwhile, PTU-HPM-Zn1/4 showed excellent antibacterial property against E. Coli. In order to expand their application as flexible and wearable sensor devices, two PTU-HPM-Zn1/4 based conductive films were prepared, which exhibited fast and stable sensing characteristics.