AsianScientist (Feb. 22, 2019) – A research group from RIKEN and Kyushu University, Japan, has developed a new type of material that is self-healing and has shape memory. They reported their findings in the Journal of the American Chemical Society.
Materials that can self-heal have become a popular area of research during the last decade, and a variety of materials have been developed. However, most of the self-healing materials reported to date have relied on sophisticated designs that incorporate chemical mechanisms into polymer networks, such as irreversible or reversible covalent bond formation, hydrogen bonding, metal-ligand interactions or ionic interactions.
The resultant materials require some external stimulus, such as heat or pressure, to prompt them to heal, and in most cases, they do not function in water, acid or alkaline solutions because the chemical networks cannot survive such conditions. The ideal is to create a material that possesses sufficient toughness and can autonomously self-heal under various conditions.
In the present study, researchers led by Professor Hou Zhaomin of the RIKEN Center for Sustainable Resource Science and the RIKEN Cluster for Pioneering Research used a catalyst based on scandium, a rare metal, to create polymers composed of alternating sequences of ethylene and anisylpropylenes and shorter ethylene-ethylene segments. These polymers ranged from soft viscoelastic materials—materials that can be elastic but also exhibit liquid-like properties—to tough elastomers which can be stretched but return to their original shapes, and rigid plastics.
The researchers demonstrated that the elastomer copolymers were very elastic and tough, showing remarkable self-healing property when subjected to mechanical damage. Remarkably, the material could self-heal not only in a dry environment, but also in water and aqueous acid and alkaline solutions, without the need for any external energy or stimulus.
“We had learned from our previous work that a scandium catalyst would be a useful way to create the copolymers of ethylene and anisylpropylenes, but we were astounded by the special properties that this class of materials exhibited. We look forward to working to find applications for these different films, which can be made easily from ethylene and other olefins,” said Hou.
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