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) (PTUEG3; Tg=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) (PTUC8; Tg=50 °C), an analogue of PTUEG3, cannot heal below 92 °C. We found that their polymer blend self‐healed in a temperature range above 32 °C even when its PTUEG3 content was only 20 mol %. Unlike PTUEG3 alone, this polymer blend, upon exposure to high humidity, barely plasticized, keeping its excellent mechanical properties due to the non‐hygroscopic nature of the PTUC8 component. CP/MAS 13C NMR analysis revealed that the polymer blend was nanophase‐separated, which possibly accounts for why such a small amount of PTUEG3 provided the polymer blend with humidity‐tolerant self‐healable properties.

Multicomponent Polymerizations of Elemental Sulfur, CH2Cl2, and Aromatic Amines toward Chemically Recyclable Functional Aromatic Polythioureas

“…Besides existing reactions, great effort in excavating the chemical properties of potential monomers and exploring new organic reactions is hence still required. For example, polythioureas are a group of sulfur-containing functional polymer materials with rapidly increasing research interests in self-healing materials, 2 heavy metal removal, 3 capacitor dielectrics, 4,5 and so on, 6 owing to their fascinating features such as self-healing capability, 7,8 strong metal coordination ability, 9 high ionic conductivity, 10 and exceptional dielectric properties. 11 The common synthetic approaches for polythioureas generally involved a similar strategy of reacting diamines with active sulfur-containing compounds including 1,1′-thiocarbonyldiimidazole, 7 thiophosgene, 4 diisothiocyanate, 4 and thiourea, 12 which were normally expensive, smelly, toxic, or required tedious synthesis, bringing difficulty and additional cost for storage and usage, and hindering the development of polythiourea materials.…”

Thiourea as a “Polar Hydrophobic” Hydrogen-Bonding Motif: Application to Highly Durable All-Underwater Adhesion

“…Serendipitously, our research on self-healing polymers has provided a solution to this challenge. In 2018, we reported a self-healing polymerglass composed of repetitive “ether thiourea” structures. − Despite being mechanically robust, this polymer unprecedentedly self-healed even at 12 °C, much lower than its glass transition temperature (27 °C) . Unlike urea, thiourea forms an irregularly shaped hydrogen-bonding (H-bonding) network that discourages unfavorable crystallization which causes brittleness of the material.…”