TAGS: Biobased Solutions
Scientists from the University of Groningen (The Netherlands) and the East China University of Science and Technology (ECUST) in Shanghai produced different polymers from lipoic acid, a natural molecule. These polymers are easily depolymerized under mild conditions.
Some 87 percent of the monomers can be recovered in their pure form and re-used to make new polymers of virgin quality.
Perfect Building Block
“
We found a way to produce polymers from the natural molecule lipoic acid in a very controlled way. It is a beautiful molecule and a perfect building block that was created by nature,” explains Ben Feringa, Professor of Organic Chemistry at the University of Groningen. The molecule has a ring structure that includes a sulphur-sulphur bond. When this bond is broken, the sulphur atoms can react with those of another monomer. This process was known before, but they found a way to control it and to create long polymers.
The molecule also has a carboxyl group, which readily reacts with metal ions. These can crosslink the polymers, which results in an elastic material. By dissolving the molecule in water with sodium hydroxide and then evaporating the water, a firmer polymer film is produced through ionic bonds.
As the polymerization is achieved through reversible bonds, the material is also self-healing. “
When it is cut, you can simply press the ends together and they will reconnect in a few minutes,” explains Feringa.
Reversible Polymerization
Most of the work in the Materials paper was carried out by Qi Zhang, first as a PhD student at ECUST in Shanghai and later as a postdoctoral researcher at the University of Groningen. Lipoic acid is a natural small molecule with an elegant structure. Simply exposing the polymers to sodium hydroxide dissolves the polymers into monomers. By adding a little acid, the monomers precipitate and can be recovered. The quality of these recycled monomers is identical to that of the original material.
Recycling Without Loss of Quality
The material can be recycled into monomers several times, without loss of quality. However, industrial applications of this new polymer are a long way off. The scientists are conducting experiments now to create polymers with new functionalities and to better understand the polymerization and depolymerization processes.
Furthermore, although 87 percent of the monomers can already be recovered, the scientists want to get as close to a hundred percent as possible.
Source: University of Groningen