Design and Application of Self-healing Polyurethanes by Controlling Hydrogen Bond Array and Disulfides
The most crucial attributes of self-healing polymers include effective recovery at room temperature and prolonged durability. However, achieving these two characteristics simultaneously proves challenging due to their inherent contradiction. In this study, a transparent and easily processable thermoplastic polyurethane (TPU) with the highest reported tensile strength and toughness is developed by manipulating the chemical structure of soft and hard segments. Notably, it features abundant carbonyl groups in its soft segments and exhibits complete amorphous character with minimal phase separation, attributed to poor hard-segment stacking. This material operates in a dual mechano-responsive mode, undergoing a reversible disorder-to-order transition in its hydrogen-bonding array. It demonstrates healing properties in static conditions and toughness enhancement in dynamic scenarios. In static mode, the non-crystalline hard segments facilitate the dynamic exchange of disordered carbonyl hydrogen bonds for self-healing. When stretched, the amorphous phase transforms into stiff crystals through a transition that orders inter-chain hydrogen bonding. Upon release, both the phase and strain fully revert to the pre-stressed state, allowing the healing process to repeat. Furthermore, colorless and transparent elastomers can be manufactured by altering the type of disulfide. Addition to the main topic, we aim to showcase various examples of sustainable plastics for the brain storming.
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