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

Abstract

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.

Disulfide-Mediated Reversible Polymerization toward Intrinsically Dynamic Smart Materials

“…This is challenging because mechanical robustness seems contradictory with dynamicity (chain mobility) in the case of a polymer network. However, a few solutions have been presented in recent studies. − …”

Carbon nanotube reinforced self-healable polythiourethane with excellent bonding strength and improved thermal conductivity

“…The dynamic chemistries were achieved based on noncovalent bonds such as metal coordination, molecular/supermolecular H-bonds, p-p stacking interactions, and so on; or dynamic covalent bonds such as S-S bonds, Se-Se bonds, Diels-Alder reactions, boronic esters, transesterification reactions, urethane/urea transcarbamoylation reactions and so on. [7][8][9][10][11][12][13][14][15][16] Qu et al introduced polymer materials with high elongation and fast self-healing performance. 17 On this basis, the mechanical properties and self-healing properties at room temperature were obviously improved by increasing the concentration of the iron ions.…”

Glassy Hybrid Network with Excellent Toughness and Self-Healing Ability at Ambient Temperature

“…Actually, it is extremely challenging to develop glassy polymers capable of self-healing in glassy state due to the frozen condition of molecular chains. [11][12][13][14][15][16][17] In a milestone work, Aida et al synthesized a poly(ether-thiourea) (TUEG 3 ) with large number of non-linear zigzag hydrogen bonds. 11 Its self-healing at room temperature can be achieved by the sliding of hydrogen bonds between molecular chains under external pressure.…”