New plastic dissolves in salt water

Scientists at the Japanese research and development agency RIKEN have unveiled a new type of plastic that’s stable in everyday use but dissolves quickly in saltwater, leaving behind only safe compounds, and no microplastics.

The benefit of plastics is that they’re made with strong covalent bonds that hold their molecules together, meaning they take a lot of energy to break. This is why they’re so sturdy and long-lasting, but they last for decades – even centuries – before fully breaking down, and even then the microplastics remain in the environment, and even in our bodies. 

The new type of plastic is made of supramolecular polymers, which have reversible bonds that function like sticky notes that can be attached, removed and reattached, according to the researchers. The team wanted to make a specific type of supramolecular polymer that would be strong enough for the usual uses of plastic but could also be made to break down quickly when required, under mild conditions and leaving only non-toxic compounds.

After screening a range of molecules, the researchers identified a particular combination with the right properties – sodium hexametaphosphate, which is a common food additive, and monomers based on guanidinium ions, which are used in fertilizers. When these two compounds are mixed together in water, they form a viscous material that can be dried to form plastics.

A reaction between the two ingredients forms “salt bridges” between the molecules that make the material strong and flexible, like conventional plastic. However, when they’re soaked in saltwater, the electrolytes unlock those bonds, and the material dissolves.

Source: newatlas.com