IT COULD spell the end of plastic pollution. A novel polymer that breaks down in response to certain chemical triggers could be the key to developing a self-destructing plastic bag.
Plastics have gained a reputation as an environmental menace as some can take hundreds of years to biodegrade, posing a danger to wildlife and clogging the seas.
Now and Wanji Seo at Pennsylvania State University in University Park have developed a self-destructing plastic that could lead to more wildlife-friendly products. Working with the polymer poly(phthalaldehyde), they attached one of two chemical end groups or 鈥渢riggers鈥� 鈥� either a silyl ether or an allyl ether 鈥� to each phthalaldehyde building block.
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When a square of the polymer was exposed at room temperature to fluoride ions, the central section, where molecules were capped with the silyl ether, underwent rapid depolymerisation and broke down. Those sections capped with the allyl ether remained unchanged (Journal of the American Chemical Society, ).
The team has also developed polymers with end groups that react with palladium and hydrogen peroxide. They are ultimately hoping to develop polymers that respond to a wide variety of chemicals, says Phillips.
Capping polymers in their entirety with an end group that responds to a specific chemical could be the basis for a low-energy method for recycling plastic waste, says Phillips. The technique could eventually give rise to plastics that degrade quickly when exposed to chemicals in the environment, he adds. If a bag made of the right plastic makes it to the ocean, for example, microbial enzymes in seawater would make the material depolymerise 鈥渁nd the bag just disappears鈥�, he says.
The work could ultimately lead to objects that can change their shape because they are made of two or more plastics that break down in response to different triggers, he says. 鈥淵ou could start with a nut, and then you could expose it to a signal and you could have a washer, and if you didn鈥檛 like that washer you could expose it to a different signal and then you have an O-ring.鈥�
The team cautions that the research is still at the proof-of-concept stage. Work remains to be done to find polymers that break down into substances that are more environmentally friendly than phthalaldehyde. Another problem is that the polymers they have so far made are sensitive to acidity and need to be made more stable to be usable, says Phillips.
Nevertheless, , a polymer physicist at the University of Reading, UK, says the work has produced an interesting new smart material. But if the process is to become truly green, the challenge will be finding trigger groups that react when exposed to common chemicals in the environment, he says.
