Plastic can be programmed to have a lifespan of days, months or years

Chemical additions to plastic that mimic natural polymers like DNA can create materials that decompose within days, months or years rather than littering the environment for centuries. The researchers hope their new technique will create plastic products that will serve their purpose and then safely self-destruct.

In 2022, more than a quarter of a billion tons of plastic were thrown away globally, and only 14% was recycled – the rest was either burned or buried. The promise of practical, biodegradable plastic has been around for at least 35 years, and efforts have been made to make such materials using everything from bamboo to algae. But in reality, many of these materials are difficult to compost and their producers make unrealistic claims.

Now Yuwei Gu and colleagues at Rutgers, State University of New Jersey, are developing a technique to create plastics with finely tuned lifespans that could quickly decompose either in compost or in the natural environment.

Gu wondered why natural, long-stranded polymers like DNA and RNA could break down relatively quickly, while synthetic polymers, like plastics, could not, and whether there was a way to replicate their process.

Natural polymers contain chemical structures called neighboring groups that facilitate deconstruction. These structures cause internal reactions called nucleophilic attacks that break the bonds of polymer chains – which requires a lot of energy with normal plastics.

Gu and his team created artificial chemical structures that mimic these neighboring groups and added them when making new plastics. They found that the resulting material could decompose easily, and that by changing the structure of the additions, they could fine-tune how long the material remained intact before deconstructing.

Once the plastic is broken down, the long polymer chains are converted into small fragments that Gu hopes will either be used to make new plastics or will dissolve safely in the environment.

“This strategy works best for plastics that benefit from controlled degradation over several days or months, so we see strong potential for applications such as food packaging and other short-lived consumer materials,” says Gu. “At the moment, it is less suitable for plastics that need to remain stable for decades before breaking down, such as building materials or long-term structural components.”

But there are still several issues to resolve before this type of plastic can be used commercially. The liquid remaining after plastic deconstruction consists of fragments of polymer chains, and further testing is needed to ensure that this soup of parts is non-toxic and therefore can be safely released into nature.

Additionally, ultraviolet light is currently required to initiate deconstruction, although ambient sunlight is sufficient. So until the group finds ways to create materials that can decompose in the dark, any buried or otherwise covered plastic will remain in the environment almost indefinitely.