Novel plastic turns into a gas when heated—then reforms once cooled

This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: In a study published in Macromolecules, researchers introduce a novel polymer that could simplify how materials are applied, removed and recycled by eliminating several complex processing steps used today. Conventional plastics such as polyethylene, used in everyday products such as plastic bags, food packaging and shampoo bottles, are persistent and not suitable for chemical recycling.

While other chemically recyclable polymers have been developed, they typically require much higher temperatures of around 150–200 degrees Celsius to break down, and the recovered material often needs additional chemical processing before it can be turned back into plastic. The Surrey team's new material is similar to polyethylene in that it is soft, insoluble and hydrophobic, but it can be heated to just 90 degrees Celsius, where it undergoes efficient depolymerization—breaking down into its individual building blocks, known as monomers. Unlike most depolymerization processes, in which the recovered monomers are liquids, Surrey's material forms a gas instead.

As the vapor cools, it spontaneously reforms into the original waterproof polymer with the same properties as before. "Most plastics are designed to be stable, which is exactly what makes them difficult to recycle or remove. We've shown that it's possible to create a material that behaves very differently—one that can transform into a vapor at relatively low temperatures before naturally rebuilding itself into the same polymer," said Dr.

Peter Roth, senior lecturer in applied organic/polymer chemistry and school postgraduate research director. "This isn't a replacement for conventional plastics, and it's certainly not a solution to the global plastic waste problem. But it does introduce a new concept that could inspire an entirely new generation of circular materials." To demonstrate the concept, the Surrey team laid out three potential applications.

First, they created waterproof polymer coatings by allowing the polymer vapor to condense onto a surface. They then showed that these coatings could be removed simply by reheating them, causing the polymer to evaporate. Finally, the researchers demonstrated that a contaminated polymer could be purified through sublimation, separating the polymer from a model additive before it reformed as a clean solid.

"The exciting part is that we've demonstrated a principle that wasn't previously available. If we can learn how to tailor this chemistry, it could eventually lead to new materials that are easier to apply, remove and recycle than many of today's plastics," said Touseef Kazmi, a postgraduate researcher at the University of Surrey and lead author of the study. The work provides a proof of concept for a new class of circular materials and could eventually enable new ways of applying and removing waterproof coatings, particularly for applications where liquid coatings struggle to cover complex surfaces.