Autonomic healing and welding by interdiffusion of dangling chains in a weak gel

Entanglement couplings of dangling chains in a weak gel are found to be applicable to the design of a self‐repairing polymer. It is confirmed that a cleavage applied using a razor blade is healed at room temperature without any manual intervention. Further, the healing efficiency is improved when the molecular weight of a prepolymer, which affects the length of dangling chains, is high. Because the healing occurs by interdiffusion of dangling chains, the relation between ambient temperature and glass transition temperature determines the time required for healing. In other words, a soft rubbery material whose glass transition temperature is lower than room temperature shows immediate healing. A weak gel whose tensile modulus is 100 MPa at room temperature, i.e. a leather‐like material, shows healing even at room temperature in a relatively short time (ca 2 h). Finally, when a weak gel shows crystallinity, healing occurs at a temperature above the melting point. Because the material has a permanent network structure, it will not show macroscopic flow even after exposure to high temperature. Copyright © 2011 Society of Chemical Industry This review focuses on self‐repairing polymers composed of a weak gel. Because of the entanglement couplings of dangling chains, a weak gel shows autonomic repairing behaviour without any manual intervention. These novel intelligent materials can be prepared using various types of crosslinked polymers.