What if plastics could simply dissolve in the ocean into natural compounds instead of remaining for hundreds of years? Scientists may have just made a significant breakthrough toward making that possible.
Scientists have been looking for sustainable alternatives to traditional plastics – known for their negative environmental effects. There are some recyclable and biodegradable options, but there are still challenges. Biodegradable plastics, like PLA, cannot break down in ocean environments because they don’t dissolve in water. This means they can still end up as microplastics—tiny fragments less than 5 mm wide—that threaten marine life and eventually make their way into the food we eat, affecting our own health.
Researchers at at the RIKEN Center for Emergent Matter Science (CEMS) wanted to address this problem by creating a form of plastic that can safely dissolve in salt water.
And that’s exactly what they achieved.
The new plastic they made is designed specifically to dissolve safely in ocean water.
How was this type of plastic made and how does it work?
The researchers combined two key ingredients:
- Sodium hexametaphosphate, a negatively charged molecule.
- Guanidinium-based molecules, which are positively charged.
When mixed in water, these two components create a network held together by salt bridges. This network create a strong yet unique plastic. As part of the process, a harmless byproduct called sodium sulfate is separated out into a watery layer, leaving behind a concentrated material that dries into a solid plastic.
Under normal conditions, this plastic is stable and durable. It’s tough enough for practical uses and can even be reshaped using heat, similar to other plastics. However, when it’s in saltwater, the salt breaks the network of bonds holding it together, causing the plastic to break apart into non-toxic components.
Takuzo Aida, who led the study, said: “While the reversable nature of the bonds in supramolecular plastics have been thought to make them weak and unstable our new materials are just the opposite.”
“With this new material, we have created a new family of plastics that are strong, stable, recyclable, can serve multiple functions, and importantly, do not generate microplastics,” Aida added.
Citation: Yiren Cheng et al. “Mechanically strong yet metabolizable supramolecular plastics by desalting upon phase separation” Science 386, 875-881 (2024). DOI:10.1126/science.ado1782
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