Mechanically Robust, Self-Healable Polymers Usable under High Humidity: Humidity-Tolerant Noncovalent Cross-Linking...

Although mechanically robust polymer materials had not been thought to self-heal, we recently found that poly(ether thiourea) PTUEG₃, which is a glassy polymer with high mechanical strength, self-heals even at ambient temperatures. This finding updated the above preconception. Nevertheless, it should also be noted that PTUEG₃, under high humidity, absorbs water and is plasticized to lose its mechanical strength. Humidity-induced plasticization is a general problem for polymers with polar groups. Herein, we report that PTUEG₃, if designed by copolymerization to contain only 10 mol % of a dicyclohexylmethane (Cy₂M) thiourea unit (TUCy₂M), serves as a humidity-tolerant, mechanically robust polymer material that can self-heal at ambient temperatures. This copolymer contained, in its ether thiourea (TUEG₃)-rich domain, a humidity-tolerant, noncovalently cross-linked 3D network with mechanical robustness formed by stacking of the Cy₂M group. The present work provides a promising design strategy for mechanically robust, self-healable polymers usable under high humidity.