Plastics are everywhere, from packaging and clothing to cars and medical devices. But their durability comes at a cost: when they break down, they release microplastics—tiny particles less than 5 millimeters wide—that pollute the oceans, harm marine life, and infiltrate the food chain. Researchers from the RIKEN Center for Emergent Matter Science In Japan may have found a solution.

A team led by Takuzo Aida developed a new kind of plastic that is strong, versatile, and biodegradable. Most importantly, it dissolves in seawater.

We suck at recycling plastic. Even now, after all these years, we recycle less than 10% of the plastic worldwide, and we keep making more of it. Not only are we bad at recycling the plastic that can be recycled, but a big chunk of our plastic production is simply unrecyclable. So we’re stuck with a conundrum: we want to use more plastic and yet we can’t dispose of it in a decent way. So what can we do?

Well, one approach is to look for bacteria for help.

Multiple teams of researchers are working on bacteria that could disintegrate and essentially eliminate plastic from the environment. There’s a lot of good progress in this field, but scaling the approach is very challenging.

Another idea is to make plastic biodegradable — this is what the new research focused on.

A plastic that melts in water

While some biodegradable plastics already exist, they often fail in marine environments. For example, polylactic acid (PLA), a widely used biodegradable plastic, does not dissolve in seawater, leaving it vulnerable to contributing to microplastic pollution. This limitation has driven scientists to search for materials that are both sustainable and effective in all environments.

Aida and his team turned to supramolecular chemistry — an emerging field in chemistry that deals with molecules tied by relatively weak forces.

They created a polymer held together by reversible interactions called salt bridges. These cross-linked structures give the plastic its strength and flexibility, but they also have a unique vulnerability: salt water. When exposed to electrolytes found in seawater, the salt bridges destabilize, allowing the plastic to dissolve into its component molecules.

“While the reversable nature of the bonds in supramolecular plastics have been thought to make them weak and unstable,” says Aida, “our new materials are just the opposite.”

In ocean water, the new plastic starts to break down within hours. It gets even better: in soil, the sheets of plastic degrade in no more than 10 days and work to fertilize the soil.

The chemistry behind it

The researchers achieved this breakthrough by combining two ionic monomers. One is sodium hexametaphosphate, a food-safe compound, and the other is a guanidinium ion-based monomer. Together, these ingredients form a stable, moldable material when the sodium sulfate byproduct is removed during production.

Without this desalting step, the resulting material is brittle and unsuitable for use. But when properly processed, the dried plastic—nicknamed alkyl SP2—exhibits properties comparable to traditional plastics. This makes it versatile for various applications while maintaining the ability to degrade safely in the ocean.

The new plastic isn’t just biodegradable; it’s also customizable. By tweaking the type of sulfate used in the manufacturing process, the researchers created versions with varying levels of hardness, flexibility, and tensile strength. These variations allow the material to serve multiple purposes, from scratch-resistant surfaces to silicone-like rubber. Basically, it’s got all the flexibility we’ve come to expect from plastics.

Additionally, the plastic is non-toxic, non-flammable, and emits no carbon dioxide during its breakdown. It can also be reshaped at temperatures above 120°C, similar to other thermoplastics. This makes it suitable for industries like 3D printing, medical devices, and consumer goods.

It’s even recyclable if that becomes relevant. When dissolved in salt water, the plastic’s components can be recovered and reused. In tests, the team recovered 91% of the hexametaphosphate and 82% of the guanidinium monomers. This efficient recycling process reduces waste and encourages circular use.

Can we scale this plastic?

The implications of this discovery are vast. Marine environments, often the final destination for plastic waste, could see a dramatic reduction in pollution. We discard around 11 million metric tons of plastics into our oceans every year, which could be greatly reduced with this new plastic.

Industries could adopt this material for single-use items like packaging, which currently account for a significant portion of ocean-bound plastic. The customizable properties also open doors for specialized uses, such as medical implants or biodegradable fishing nets.

However, the research is still in its early stages.

Manufacturing processes must be scaled up and streamlined to compete with the low costs of conventional plastics. Public and industrial acceptance will also play a role, requiring clear communication about the material’s benefits and limitations. Basically, the price of this new plastic has to be comparable, otherwise many companies simply won’t switch to it. Ultimately, this cost and scalability end up being the biggest obstacles in the deployment of sustainable plastic alternatives.

Yet we cannot afford to simply delay this more and more.

Plastic pollution is one of the most pressing environmental issues of our time, and solving it requires innovative solutions. Aida and his team have taken a significant step forward. We have the scientific foundation for better, more sustainable materials.

The study was published in Science.