Self-sealing is a different concept comparing with self-healing. In fact, the healing processes found in living organisms closely to the process of self-sealing rather than self-healing. In other words, the healing in living creature mainly occurs at a surface level preserving a variety of wet internal contents maintain unique softness (i.e. wound healing). Researchers have extensively studied self-healing materials, which are classified as both intrinsic and extrinsic healing systems. Most of intrinsic systems repair the damage using reversible bonds or non-covalent bonds. However, they require external stimulus such as light, heat, moisture, and pressure to trigger the reactions at the damage. In contrast, for extrinsic healing systems, they require some extrinsic catalysts and healing agents typically encapsulated in matrix. The matrix of the materials includes the spreading catalysts and capsules with healing agents, which can be activated by the catalysts. However, the embedding process of capsules is difficult and complicate. Herein, we developed a new regenerative self-sealing material with no aid of external stimulus and additives inspired by insect wound healing and fruits browning processes. Insect and some fruits have catechol derivatives and phenol oxidases, which can oxidize the catechol derivatives when exposed to air (i.e. ambient oxygen). Among them, pyrogallol (PG) was chosen due to its high reactivity to oxygen, which can be oxidized by ambient oxygen without need of enzymes. PG and polyehtylenimine (PEI) form the film at liquid/air interface. When the film was torn or peeled-off, the damaged site was inevitably exposed to air. As a result, PG under the film was activated and regenerated new film, which stuck to the existing film and self-sealed the damage within 20 minutes. There was no need of external stimulus and embedding process for healing. In addition, the film can be self-healed unlimitedly as long as the liquid-phase exists, and the recovered area showed the same mechanical properties even after 40 cycles as the original one.

Air-triggered self-sealing polymeric materials spontaneously formed at liquid/air interface

253rd National Meeting (2017)

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