Scientists develop plastics that can break down, tackling pollution

(Press-News.org) Yuwei Gu was hiking through Bear Mountain State Park in New York when inspiration struck.

Plastic bottles littered the trail and more floated on a nearby lake. The jarring sight in such a pristine environment made the Rutgers chemist stop in his tracks. Nature makes plenty of long-stranded molecules called polymers, including DNA and RNA, yet those natural polymers eventually break down. Synthetic polymers such as plastics don’t. Why?

“Biology uses polymers everywhere, such as proteins, DNA, RNA and cellulose, yet nature never faces the kind of long-term accumulation problems we see with synthetic plastics,” said Gu, an assistant professor in the Department of Chemistry and Chemical Biology in the Rutgers School of Arts and Sciences.

As he stood in the woods, the answer came to him.

“The difference has to lie in chemistry,” he said.

If nature can build polymers that serve their purpose and then disappear, Gu reasoned, perhaps human-made plastics could be made to do the same. Gu already knew that natural polymers contain tiny helper groups built into their structure that make chemical bonds easier to break when the time is right.

“I thought, what if we copy that structural trick?” he said. “Could we make human-made plastics behave the same way?”

The idea worked. In a study published in Nature Chemistry, Gu and a team of Rutgers scientists have shown that by borrowing this principle from nature, they can create plastics that break down under everyday conditions without heat or harsh chemicals.

“We wanted to tackle one of the biggest challenges of modern plastics,” Gu said. “Our goal was to find a new chemical strategy that would allow plastics to degrade naturally under everyday conditions without the need for special treatments.”

A polymer is a substance made of many repeating units linked together, like beads on a string. Plastics are polymers, and so are natural materials such as DNA, RNA and proteins. DNA and RNA are polymers because they are long chains of smaller units called nucleotides. Proteins are polymers made of amino acids.

Chemical bonds are the “glue” that holds atoms together in molecules. In polymers, these bonds connect each building block to the next. Strong bonds make plastics durable, but they make them difficult to break down. Gu’s research focused on making these bonds easier to break when needed, without weakening the material during use.

The advance does more than make plastics degradable: It makes the process programmable.

The key to the discovery was how the researchers arranged components of the plastic’s chemical structure so they were in the perfect position to start breaking down when triggered.

The process can be likened to folding a piece of paper, so it tears easily along the crease. By “pre-folding” the structure, the plastic can break apart thousands of times faster than normal. Even though the plastic is easier to break when activated, its basic chemical makeup stays the same, so it remains strong and useful until the moment the user wants it to degrade.

“Most importantly, we found that the exact spatial arrangement of these neighboring groups dramatically changes how fast the polymer degrades,” Gu said. “By controlling their orientation and positioning, we can engineer the same plastic to break down over days, months or even years.”

This fine-tuning capability means different products can have lifetimes matched to their purpose. Take-out food packaging might only need to last a day before it disintegrates, while car parts must endure for years. The team demonstrated that breakdown can be built-in or can be switched on or off using ultraviolet light or metal ions, adding another layer of control.

The implications go beyond solving the global plastics crisis. Gu said the principle could enable innovations such as timed drug-release capsules and self-erasing coatings.

“This research not only opens the door to more environmentally responsible plastics but also broadens the toolbox for designing smart, responsive polymer-based materials across many fields,” he said.

For Gu, the ultimate goal is clear: Plastics should serve their purpose and then disappear.

“Our strategy provides a practical, chemistry-based way to redesign these materials so they can still perform well during use but then break down naturally afterward,” he said.

Early lab tests have shown that the liquid produced by the breakdown is not toxic. But Gu said that more research needs to be done to ensure that is the case.

Looking back, Gu said he was surprised that the idea sparked on a quiet mountain trail actually worked.

“It was a simple thought, to copy nature’s structure to accomplish the same goal,” he said. “But seeing it succeed was incredible.”

Gu and his team are now taking their research in several new directions.

They are studying in detail whether the tiny pieces that plastics break down into are harmful to living things or the environment. This will help make sure the materials are safe for their entire life cycle.

The team also is looking at how their chemical process could work with regular plastics and fit into current manufacturing methods. At the same time, they are testing whether this approach can be used to make capsules that release medicine at controlled times.

There are still a few technical challenges, but Gu said that with more development, along with working with plastic makers who understand the need for sustainable plastics, their chemistry could eventually be used in everyday products.

Other Rutgers scientists who contributed to the study included: Shaozhen Yin, a doctoral student in the Gu lab who is first author on the paper; Lu Wang, an associate professor in the Department of Chemistry and Chemical Biology; Rui Zhang, a doctoral student in Wang’s lab; N. Sanjeeva Murthy, a research associate professor at the Laboratory for Biomaterials Research; and Ruihao Zhou, a former visiting undergraduate student.

Explore more of the ways Rutgers research is shaping the future

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