Plastics are strong and durable, which makes them great for everyday use. But this durability becomes a problem when they end up in nature. Traditional plastics take a long time to break down—sometimes hundreds of years—and during that time, they can harm wildlife and humans through tiny plastic particles, called microplastics.
To address this issue, Japan researchers of Takuzo Aida at the RIKEN Center for Emergent Matter Science (CEMS) have created a new kind of plastic that remains strong during use but dissolves rapidly in saltwater. Once it dissolves, the plastic breaks down into safe, non-harmful compounds, helping to reduce its environmental impact, reports NDTV.
The new plastics were made by combining two ionic monomers that form cross-linked salt bridges, which provide strength and flexibility.
In the initial tests, one of the monomers was a common food additive called sodium hexametaphosphate and the other was any of several guanidinium ion-based monomers.
Both monomers can be metabolized by bacteria, ensuring biodegradability once the plastic is dissolved into its components.
"While the reversable nature of the bonds in supramolecular plastics have been thought to make them weak and unstable," says Aida, "our new materials are just the opposite."
In the new material, the salt bridges structure is irreversible unless exposed to electrolytes like those found in seawater. The key discovery was how to create these selectively irreversible cross links.
As with oil with water, after mixing the two monomers together in water, the researchers observed two separated liquids. One was thick and viscous and contained the important structural cross linked salt bridges, while the other was watery and contained salt ions. For example, when sodium hexametaphosphate and alkyl diguanidinium sulfate were used, sodium sulphate salt was expelled into the watery layer. The final plastic, alkyl SP2, was made by drying what remained in the thick viscous liquid layer.
Bd-pratidin English/ Afia
