By: Mimi Martinez
Each year, around 11 million metric tons of plastic end up in the ocean. This is roughly equivalent to dumping a full garbage truck of plastic into the sea every minute.[i]
Solving this crisis requires a multi-pronged approach with practices including improving global waste disposal systems, cutting back on single-use plastics, and introducing innovative materials. A particularly promising addition to this toolkit is a new kind of water-soluble plastic that degrades rapidly in ocean water and breaks down quickly on land.
Researchers at the RIKEN Center for Emergent Matter Science (CEMS) in Japan have developed a plastic that combines two ionic monomers.[ii] Ionic components, carrying positive and negative charges, are water-soluble and commonly used in applications such as polymer electrolytes. When combined, these monomers create crosslinked salt bridges that provide both strength and flexibility to the plastic.
The early stages of the research used two monomers that could be metabolized by bacteria. These were designed to create reversible bonds that would biodegrade under specific conditions. However, this version was unstable and prone to breaking down too easily.
To refine the material, researchers added a desalination step to the process. This stage helps prevent the dried plastic from becoming a brittle crystal, preserving its usability and strength. Additionally, the team improved the formulation by using new materials that only break down in the presence of electrolytes, such as those in saltwater, making the plastic more durable during use conditions while still degradable in electrolyte heavy environments.
The final version of the plastic is non-toxic, non-flammable, and emits zero carbon during breakdown. It can be reshaped at temperatures above 120°C, similar to conventionally used thermoplastics. By experimenting with different guanidinium sulfates, a class of base sulfates, the researchers were able to tune the plastic’s hardness and tensile strength. This allows for a wide range of potential applications, from rubber-like flexible materials to strong, load-bearing plastics.
When exposed to salt water, the plastic begins to destabilize within hours, allowing it to dissolve under specific conditions. The recovery rate for the decomposed material is impressive: 91% for the first monomer (sodium hexametaphosphate) and 85% for the second (guanidinium sulfate), both of which can be recollected as powders.
On land, the plastic also biodegrades effectively. When buried in soil with phosphorus and nitrogen concentrations similar to that found in fertilizers, the material fully biodegrades in just 10 days.[iii]
This breakthrough opens the door to a more resilient and adaptive approach to reducing plastic pollution—one that not only prevents plastics from persisting in the environment but also returns them safely to nature.
[i] https://www.pew.org/en/trend/archive/winter-2022/our-ocean-is-choking-on-plastic-but-its-a-problem-we-can-solve#:~:text=Some%2011%20million%20metric%20tons,by%202040%20without%20ambitious%20action.
[ii] https://www.science.org/doi/10.1126/science.ado1782
[iii] https://www.riken.jp/en/news_pubs/research_news/pr/2024/20241122_1/
