Thermal- and mechanical-responsive polyurethane elastomers with self-healing, mechanical-reinforced, and thermal-stable capabilities

Abstract

Previous studies have shown that the commonly used Diels-Alder (DA) bonds (furan and maleimide) cleaved at low temperatures (about 100 °C), which limits further application of these self-healing materials at higher temperatures. Hence, a series of thermo stable self-healing polyurethane elastomers (PUAn-DA-x) have been developed by using the reversible DA/retro-DA reactions initiated by thermal and mechanical stimuli between anthryl and maleimide functions. The synthesized linear polyurethane bearing pendant anthryl groups (PUAn-0) was effectively toward DA reactions with a bismaleimide crosslinker (BMI) to get covalently crosslinked PUAn-DA-x networks. Tensile test showed that the stress at break of PUAn-DA-1/1 was increased by more than 261% after the PUAn-0 was effectively networked by DA bonds. At the same time, with the aid of hydrogen bonds and chains’ rearrangement, the healing efficiency of PUAn-DA-1/1 could reach as high as 91.28% via the recombination of mechanically decoupled anthracene and maleimide without causing deformation of bulk specimens. In addition, the thermal stabilities of the DA bonds and PUAn-DA-x were studied.