Dissolvable Plastic: RIKEN’s Solution to Ocean Microplastics

There is something of an ‘out of sight, out of mind’ mentality when it comes to plastic pollution. It goes in the recycling bin, and we assume that’s that.

Shockingly, though, only around 9% of plastic around the world is actually recycled. The rest ends up in landfill, incinerators or nature.

The final destination for lots of plastic is the ocean. The equivalent of a dump truck full of plastic pollutes our oceans every single minute according to the World Economic Forum. It says that there may be more pieces of plastic in the ocean than there are fish by the year 2050.

A team of Japanese researchers have made a significant breakthrough in the fight against plastic pollution by developing a new type of plastic that dissolves completely in seawater. 

This innovative material was created by scientists at the RIKEN Center for Emergent Matter Science and uses supramolecular chemistry that allows it to biodegrade or be recycled.

How dissolvable plastic is made

The plastic is based on supramolecular chemistry, using ionic monomers linked by reversible salt bonds. This unique structure allows the plastic to maintain its strength during use while enabling rapid degradation when exposed to saline environments. 

According to Lead Researcher Takuzo Aida: “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.

“Plastics, especially polyethylene terephthalate, which is used in bottles, are incredibly versatile. They are flexible but strong, durable and recyclable. It’s hard to beat that convenience.”

The reversible nature of supramolecular polymer bonds also have a weakness as they can disintegrate too easily, previously limiting their applications. 

Sodium hexametaphosphate, a common food additive, and guanidinium ion-based monomers, used in fertilisers and soil conditioners, help RIKEN's material stay together with strong cross-linked bonds.

In the study, the researchers produced a small sheet of this supramolecular material by mixing the compounds in water. 

This separated into two layers, the lower containing the compounds bound with salt bridges. The bottom layer was then separated and dried to create a plastic-like sheet.

The sheet can even be made waterproof with a hydrophobic coating and can dissolve just as quickly when its surface is scratched.

The properties of dissolvable plastic

Tests have shown that the plastic begins to break down within hours in seawater and decomposes completely in soil within ten days, releasing nutrients similar to fertiliser that can benefit plant life. 

More than 90% of the primary component used can be recovered after dissolution, making it highly recyclable.

These plastics aren’t just for niche uses either. The material can be moulded into various forms like traditional thermoplastics, exhibiting strength and versatility comparable to conventional plastics.

Addressing the microplastic problem

When plastic degrades, it breaks down into smaller fragments known as microplastics. These can contaminate food chains and could cause harm to organisms and animals by carrying potentially harmful chemicals.

Existing biodegradable plastics can fail to degrade effectively in marine environments or leave behind harmful residues. 

The Japanese researchers' new material offers a promising solution by ensuring complete dissolution without contributing to microplastic pollution.

When broken down, RIKEN's plastic leaves behind nitrogen and phosphorus which microbes can metabolise and plants can absorb.

Will it be rolled out globally?

Experts are optimistic about the potential for this technology to be implemented globally.

Joaquín Martínez Urreaga from the Polytechnic University of Madrid described the development as “a promising alternative to tackle marine pollution”. 

The hope is that this new type of plastic could be adopted across various industries, particularly those reliant on single-use packaging.

Nevertheless, transitioning from traditional plastics to this new biodegradable option will require collaboration between researchers, manufacturers and policymakers. The challenge lies not only in producing this material at scale but also in creating an infrastructure that supports its use and recycling.