Researchers Discover Plastic That Breaks Down Fastest in Seawater

The world’s oceans are absorbing an estimated millions of tons of plastic waste each year. From floating garbage patches to microscopic plastic particles embedded in marine food chains, plastic pollution has become one of the defining environmental crises of the 21st century. Microplastics have been detected in plankton, fish, seabirds and even in seafood consumed by humans, raising growing ecological and health concerns.

Against this backdrop, researchers at Northwestern University have developed a material designed to address one of the core problems: plastic that persists for decades or centuries in marine environments. Their study was published in December 2025 in the Journal of the American Chemical Society. The research introduces a cellulose-based plastic engineered to degrade in seawater without leaving behind harmful microplastic residues.

Lead author Zhenghong Chen said the team aimed to design a material that maintains the mechanical performance of conventional plastics while fundamentally changing its environmental fate.

Rethinking Plastic Through Supramolecular Chemistry

Traditional plastics such as polyethylene and polypropylene are derived from petroleum and designed for durability. That durability, while useful in consumer applications, becomes a liability in marine ecosystems. The Northwestern team approached the problem from a different angle: building plastic from cellulose, one of the most abundant natural polymers on Earth.

At the core of the innovation is a process known as supramolecular ionic polymerization. The researchers used carboxymethyl cellulose (CMC), a negatively charged cellulose derivative, and combined it with positively charged polyguanidinium ions. The electrostatic attraction between these oppositely charged polymers forms a stable ionic network, creating a solid plastic material.

Initially, the resulting material was mechanically strong but brittle. To improve flexibility, the researchers introduced choline chloride (ChCl) as a plasticizer. This small molecule inserts itself between polymer chains, reducing rigidity while preserving structural integrity.

“By adjusting the ratio between the ionic components and the plasticizer, we can tune the mechanical properties of the material,” Chen that came from University of Tokyo explained. “That allows us to design plastics that range from rigid to flexible, depending on the intended application.”

The ability to tailor properties is crucial if biodegradable materials are to replace conventional plastics in packaging, bags or other single-use products.

Mechanical Strength and Seawater Degradation

Laboratory testing showed that the cellulose-based material exhibits a high Young’s modulus, indicating strong resistance to deformation under stress. The addition of choline chloride significantly increased elongation capacity, improving flexibility without sacrificing strength.

However, the defining characteristic of the material is its behavior in marine conditions. When immersed in simulated seawater, thin films of the plastic gradually degraded over a period of weeks to months, depending on environmental factors such as temperature and microbial activity.

Unlike petroleum-based plastics, which fragment into microplastics that persist in ecosystems, the cellulose-based material breaks down into components that are water-soluble and environmentally benign. This distinction addresses a central concern in marine pollution, the accumulation of microscopic plastic particles that infiltrate food webs.

Chen noted that while laboratory simulations provide controlled conditions, real-world degradation rates would vary. Still, the findings suggest that designing plastics with built-in marine degradability is scientifically achievable.

Ecological and Industrial Implications

The development of a seawater-degradable plastic carries implications beyond material science. Marine plastic pollution has economic and social consequences, affecting fisheries, tourism and coastal communities worldwide. Materials that degrade safely in ocean environments could reduce long-term ecological damage in cases where plastic waste escapes waste management systems.

The use of cellulose as a primary feedstock also aligns with circular economy principles. Cellulose can be sourced from agricultural residues, sustainably managed forests or recycled paper products. This reduces reliance on fossil fuels and lowers the carbon footprint associated with conventional plastic production.

However, the researchers emphasize that biodegradable plastic is not a standalone solution. Marine degradation addresses the consequences of leakage into oceans, but it does not eliminate the environmental costs associated with overproduction and overconsumption.

Reducing Plastic Waste at the Source

While the development of cellulose-based plastic represents a significant step forward, Howard cautioned that innovation at the material level must be accompanied by systemic changes upstream.

“Designing plastics that degrade more safely in the environment is important,” Chen said. “But reducing the amount of plastic entering the waste stream in the first place remains critical.”

Efforts to limit single-use plastics, expand recycling infrastructure and encourage reuse are essential components of addressing marine pollution. Even biodegradable materials require energy and resources to produce, and large-scale manufacturing carries environmental trade-offs.

The study underscores a broader shift in materials research, designing products with their entire life cycle in mind. Rather than optimizing solely for durability and cost, scientists are increasingly integrating environmental end-of-life scenarios into the design phase. (Wage Erlangga)