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: What if the key to making stronger, more sustainable plastics isn't changing their ingredients, but rearranging their molecules? Virginia Tech researchers have put that idea to the test, creating degradable polymers with a new molecular architecture that combines properties often difficult to achieve in one material: strength, toughness, flexibility and the ability to block oxygen.
The findings could have implications for food packaging, which needs to keep oxygen out while remaining strong and flexible enough to withstand processing, transportation and storage. By rearranging polymer chains into rings, the researchers created materials that blocked oxygen as effectively as a widely studied biodegradable plastic while being significantly tougher and better able to stretch without breaking. The work, led by Rong Tong, professor of chemical engineering, in collaboration with Yifan Cheng, assistant professor of food science and technology, was published in Nature Communications.
Most conventional plastics consist of long, linear molecular chains. The research team, which included Ph.D. students Ziyu Huo, Xiaoyu Xie and Huida Duan, altered the plastics' molecular architecture. The researchers joined the ends of polymer chains to form continuous rings.
They also controlled the sequence of the molecules within each ring, gradually changing the composition from one type of building block to another to create what researchers call a "gradient" polymer. The resulting polymers had properties that are often difficult to achieve together. "By controlling both the shape and the sequence, we are able to make materials that are strong, tough, flexible and good at blocking oxygen," Tong said.
One material recovered much of its shape after being stretched and fractured. Tong said the combination of strength and toughness was particularly surprising. "Usually, when you improve the strength of a material, you have to make some sacrifices—the material could become more brittle, for example," he said.
"But here, we see both the strength and the toughness improve together. That shows us that the ring-shaped structure and the controlled arrangement work together in a way we haven't seen in previous approaches." Several of these cyclic polymers showed oxygen-barrier properties comparable to polylactic acid, or PLA, a widely studied biodegradable plastic. PLA blocks oxygen well, an important property for food packaging because oxygen exposure can degrade food.
Extract — continue reading at the source.
