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Research institute Riken develops self-healing polymer with shape memory

TOKYO -- A team at the Riken research institute in Wako, Saitama Prefecture north of Tokyo has developed a polymer that can be cut and rejoined, and behave like rubber or plastic depending on the temperature.

The water in a bag made of a newly developed polymer doesn't leak even when pierced by a needle. (Photo courtesy of Riken)

Hou Zhaomin, a group director of the institute who led the research, commented, "The material can be used in various ways and we expect it will be applied in a broad range of industries." The polymer can be synthesized cheaply and easily in large quantities.

The polymer has a structure in which many organic compounds are connected. To create it, the researchers synthesized substances called anisylpropylenes and ethylene using a catalyst they developed.

The material can spontaneously self-heal in a variety of mediums including water and acidic and alkali solutions. When severed surfaces are brought together, they return to the original joined state in about 5 minutes. When a water bag made of the material is pierced by a needle, the hole heals itself, stopping the water from leaking.

The team also designed the material to have shape memory through the action of another organic compound. When the shape of the material is changed in hot water at 50 degrees Celsius and the material is then returned to room temperature, it keeps its form. When it enters the hot water again, it returns to its original shape. This is the result of lively interaction between the molecules that make up the polymer, Hou says.

The research was published in the Journal of the American Chemical Society on Feb. 7.

(Japanese original by Yui Shuzo, Science & Environment News Department)

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