Mechanically robust self-repairing polyurea elastomers: The roles of hard segment content and ordered/disordered hydrogen-bonding arrays

Abstract

It has been a challenge to impart high strength and toughness to room-temperature self-repairing polyurethane/polyurea materials. We report a room-temperature self-repairing thermoplastic polyurea elastomer (PU) with mechanical robustness. When thiosemicarbazide was used as a chain extender, strong (or weak) hydrogen bonds were formed between CO (or CS) and NH groups in the hard regions of PU. The results were optimized mechanical and self-repairing properties: the tensile strength, elongation at break, toughness, and self-repairing efficiency of the PU reached 4.43 MPa, 1498.37%, 55.14 MJ m−3, and 96.3%, respectively. We found that the increase of hard segments led to increased/decreased number of ordered/disordered hydrogen bonds, as well as enhancement of both the aggregation of hard segments and the degree of microphase separation. We proposed a model dealing with the relation between the hard segment content and the hydrogen-bonding arrays and explored the exchange rate and the order–disorder transition of hydrogen bonds, to provide an insight into the optimization of mechanical and self-repairing properties.