Self-Healing of Polymer in Acidic Water toward Strength Restoration through the Synergistic Effect of Hydrophilic and Hydrophobic Interactions.

To improve reliability, durability, and reworkability of bulk polymers utilized in ubiquitous acidic water, the authors develop a novel hyperbranched polymer capable of self-healing and recycling in a low-pH aqueous environment. The hyperbranched polymer has many hydrophilic and hydrophobic terminal groups. When it is damaged in acidic water, the hydrophilic groups are protonated, forming hydrogen bonds, and closing the crack. Meanwhile, hydrophobic interactions of hydrophobic groups are gradually established across the interface because of the intimate contact of the cracked surface, further reinforcing the rebonded portion. The amphiphilic structure proves to meet both the thermodynamic and kinetic requirements for autonomous rehabilitation. As a result, the unfavored water, which used to impede adhesion between hydrophobic polymeric materials, turns into a positive aid to crack healing. The mechanism involved is carefully analyzed and verified in terms of micro- and macroscopic techniques. The proposed operating environment-oriented design of the stimulus-responsive macromolecule may help to broaden the family of underwater self-healing polymers and their application scope.