Think of plastic as a three-dimensional puzzle: each piece fits perfectly with the others to create a solid and resistant structure. Now, thanks to chemistry supramolecular, these pieces can be engineered to separate when they come into contact with salt water. This is the principle behind a new generation of plastics that promises to solve one of the most pressing environmental problems of our time: microplastic pollution in the oceans.
The Supramolecular Breakthrough in Plastics
Traditional plastic is everywhere. For better or worse, it has shaped our modern world. But the price we pay for its convenience is high: widespread pollution and microplastics that threaten marine ecosystems. A team of researchers from RIKEN, the Japanese multidisciplinary research institute, decided to tackle this problem with an innovative approach. They developed a supramolecular plastic that retains all the positive characteristics of traditional materials, but with one key difference: it dissolves completely in salt water.
The research, published today in the journal Science (I link it to you here), opens up new perspectives in the fight against plastic pollution. But let's not fool ourselves: the real solution would be to consume less, much less.
How it works
The secret lies in the salt bridges, molecular links that in some cases give strength and flexibility to the material. These bonds are incredibly stable under normal conditions, but dissolve when they come into contact with electrolytes present in seawater. The researchers used two ionic monomers: thesodium hexametaphosphate, a common food additive, and various ion-based monomers guanidiniumThe key process occurs during cross-linking1, which creates cross-links between the polymer chains, giving the material specific properties.
When the material is immersed in salt water, these bonds reverse and the structure destabilizes within a few hours. It is as if we have created a sand castle that remains standing until the wave arrives.
Supramolecular Chemistry, Versatility and Customization
Supramolecular chemistry allows to obtain plastics with different mechanical characteristics. It is possible to create hard and scratch-resistant materials, silicone-like elastomers, weight-resistant plastics or flexible materials with low tensile strength. All these materials are non-toxic e not flammable, which means zero CO2 emissions. They can be reshaped at temperatures above 120°C like other thermoplastics. Tests have shown that mechanical properties are comparable or superior to those of conventional plastics. It's like having a superplastic that knows when to disappear.
The complete cycle
Recyclability is impressive: after dissolving in salt water, 91% of the hexametaphosphate and 82% of the guanidinium can be recovered in powder form. In soil, sheets of this new plastic degrade completely in 10 days.
But there's more: during degradation, the material releases phosphorus and nitrogen, acting as a natural fertilizer. It is a perfect example of a circular economy, where even “waste” becomes a resource. Takuzō Aida and his team have created something extraordinary. But let's remember that real innovation would be learning to live with less plastic, not just better plastic.
Future perspectives
This technology opens up interesting scenarios for medical applications and 3D printing. Researchers have also created ocean-degradable plastics using polysaccharides that form salt bridges with guanidinium monomers. But let's not be lulled by the illusion that technology will solve all our problems. The real challenge is cultural: we need to rethink our relationship with disposable materials.
Supramolecular plastic is a step in the right direction, but I want to repeat: the real progress will be when we learn to live without depending so much on plastic, of any kind.
- Crosslinking is a chemical process in which molecules of a material, usually a polymer, join together to form a three-dimensional network. ↩︎
