In a groundbreaking development, researchers led by Takuzo Aida at the RIKEN Center for Emergent Matter Science (CEMS) have created a durable plastic that promises to combat microplastic pollution in our oceans. Unlike conventional plastics, this new material is not only recyclable and biodegradable but also breaks down in seawater. The team’s findings, published on November 22 in Science, highlight a significant leap toward sustainable materials.
The Problem with Current Plastics
Plastics have long been a cornerstone of modern convenience, but their environmental impact is undeniable. Traditional plastics are non-sustainable and contribute to widespread pollution, particularly in the form of microplastics—tiny particles less than 5 mm in size. These microplastics accumulate in oceans, soil, and ultimately, the food chain, posing risks to aquatic life and human health.
While biodegradable plastics such as PLA exist, they often fail to degrade in aquatic environments due to their water-insoluble nature. This limitation has driven scientists to seek innovative solutions that address both durability and degradability.
A New Class of Plastic
The research team focused on developing supramolecular plastics—polymers held together by reversible interactions. The new plastic is crafted from two ionic monomers: sodium hexametaphosphate, a common food additive, and guanidinium ion-based monomers. These monomers form cross-linked salt bridges, providing the material with strength and flexibility while ensuring biodegradability.
“While the reversible nature of bonds in supramolecular plastics was once thought to make them weak and unstable, our new materials are just the opposite,” explained Aida. The team discovered that these cross-linked salt bridges remain stable until exposed to electrolytes like those in seawater. Once in salt water, the plastic’s structure destabilizes, breaking it down into biodegradable components.
Innovative Production Process
The production of the new plastic involved a critical “desalting” step. When the monomers were mixed in water, two distinct liquid layers formed: a thick, viscous layer containing structural salt bridges and a watery layer containing expelled salt ions. By drying the viscous layer, the team created a durable material named alkyl SP2.
Without the desalting process, the resulting plastic would crystallize into a brittle, unusable material. However, when exposed to salt water, the plastic’s structure reverses within hours, making it fully ocean-degradable. This innovative approach allows the material to combine durability with controlled degradability.
Versatility and Applications
The new plastics exhibit properties comparable or superior to conventional plastics. They are non-toxic, non-flammable (no CO2 emissions), and can be reshaped at temperatures above 120°C like thermoplastics. By varying the type of guanidinium sulfate used, the researchers created a range of plastics with different hardness levels and tensile strengths—from scratch-resistant hard plastics to flexible, rubber-like materials.
Potential applications for these plastics are vast. They can be tailored for 3D printing, medical devices, or health-related uses. Additionally, the researchers developed polysaccharide-based ocean-degradable plastics, further expanding the possibilities for eco-friendly materials.
Recyclability and Biodegradability
Recycling and biodegradability are key strengths of the new plastic. When dissolved in salt water, 91% of the hexametaphosphate and 82% of the guanidinium were recovered as powders, demonstrating efficient recycling potential. In soil, sheets of the plastic degraded entirely within 10 days, enriching the soil with essential nutrients like phosphorus and nitrogen, akin to fertilizer.
A Step Toward Sustainability
“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,” said Aida.
This revolutionary plastic offers a sustainable alternative to conventional materials, paving the way for a cleaner, healthier environment. As the world grapples with the challenges of plastic pollution, innovations like this represent a crucial step toward safeguarding our oceans and ecosystems.