Blending to Make Nonhealable Polymers Healable: Nanophase Separation Observed by CP/MAS 13C NMR Analysis

Abstract Can commodity polymers are made to be healable just by blending with self‐healable polymers? Here we report the first study on the fundamental aspect of this practically challenging issue. Poly(ether thiourea) (PTUEG 3 ; T g =27 °C) reported in 2018 is extraordinary in that it is mechanically robust but can self‐heal even at 12 °C. In contrast, poly(octamethylene thiourea) (PTUC 8 ; T g =50 °C), an analogue of PTUEG 3 , cannot heal below 92 °C. We found that their polymer blend self‐healed in a temperature range above 32 °C even when its PTUEG 3 content was only 20 mol %. Unlike PTUEG 3 alone, this polymer blend, upon exposure to high humidity, barely plasticized, keeping its excellent mechanical properties due to the non‐hygroscopic nature of the PTUC 8 component. CP/MAS 13 C NMR analysis revealed that the polymer blend was nanophase‐separated, which possibly accounts for why such a small amount of PTUEG 3 provided the polymer blend with humidity‐tolerant self‐healable properties.