Traditional plastics are harmful to the environment because they are made from non-renewable petrochemicals, require high temperatures and toxic chemicals to manufacture, and take hundreds of years to degrade. Only a small percentage of them are recycled, with the rest being disposed of in landfills, incinerated or polluting the environment .
Alternative plastics derived from plant sources such as corn starch and seaweed are gaining popularity due to their renewable and biodegradable nature. However, they are energy intensive to manufacture and difficult to recycle.
Dayong Yang and his colleagues at Tianjin University in China have developed a plastic that addresses these issues. It is synthesized by covalently bonding small strands of DNA to a chemical derived from vegetable oil, resulting in a soft, gel-like material. The gel can be molded into molds and then solidified through a freeze-drying process that extracts moisture from thegel at extremely low temperatures.
The researchers created a glass (pictured above), a triangular prism, puzzle pieces and a model of a DNA molecule (pictured below) using this technique. They then recycled these items by soaking them in water to turn them back into a gel that could be reshaped.
"What I really like about this plastic is that it can be broken down and reassembled," says Damian Laird of Australia's Murdoch University. "Although most research has focused on developing biodegradable bioplastics, if we are serious about moving towards an active economy, we must also be able to recycle them."
Image: Dayong Yang at Tianjin University/China
Another advantage of the new plastic is its wide availability of the raw material, since the Earth contains about 50 billion tons of DNA. Yang and his colleagues extracted DNA from salmon sperm, but he notes that it could also be obtained from renewable sources, such as crop waste, algae or bacteria.
Because DNA plastic is not produced at high temperatures, it emits 97 percent less carbon dioxide than polystyrene plastic and can be degraded using DNA digestion enzymes when it is no longer needed, according to Yang.
"As far as we know, our DNA plastics are the most sustainable materials known," he says.
The two main disadvantages of the plastic are that it is not as strong as traditional petrochemical plastics and that it must remain dry to prevent reversion to a gel. As a result, Yang believes it is more suitable for applications such as packaging materials and electronic devices.
Maryam Naebe of Deakin University in Australia suggests that the DNA plastic could be made waterproof by coating it with tough chemicals, like we do with paper cups. And Yang says his team intends to use the plastic to create commercial products. "This is just the beginning," he says.
The research was published in the Journal of the American Chemical Society.