Apparently it breaks down to a food additive and a fertilizer..
https://ancillary-proxy.atarimworker.io?url=https%3A%2F%2Fwww.riken.jp%2Fen%2Fnews_p...
After screening various molecules, the team found that a combination of sodium hexametaphosphate (a common food additive) and guanidinium ion-based monomers (used for fertilizers and soil conditioners) formed ‘salt bridges’ that bind the compounds together with strong cross-linked bonds. These types of bonds serve as the ‘lock’, providing the material with strength and flexibility, explains Aida.
“Screening molecules can be like looking for a needle in a haystack,” he says. “But we found the combination early on, which made us think, ‘This could actually work’.”
In their study, Aida’s team produced a small sheet of this supramolecular material by mixing the compounds in water. The solution separated into two layers, the bottom viscous and the top watery, a spontaneous reaction that surprised the team. The viscous bottom layer contained the compounds bound with salt bridges. This layer was extracted and dried to create a plastic-like sheet.
The sheet was not only as strong as conventional plastics, but also non-flammable, colorless and transparent, giving it great versatility. Importantly, the sheets degraded back into raw materials when soaked in salt water, as the electrolytes in the salt water opened the salt bridge ‘locks’. The team’s experiments showed that their sheets disintegrated in salt water after 8 and a half hours.
The sheet can also be made waterproof with a hydrophobic coating. Even when waterproofed, the team found that the material can dissolve just as quickly as non-coated sheets if its surface is scratched to allow the salt to penetrate, says Aida.
https://ancillary-proxy.atarimworker.io?url=https%3A%2F%2Fwww.science.org%2Fdoi%2F10...
Editor’s summary
A strong, glassy supramolecular polymer has been shown to prevent the formation of marine microplastics by slowly dissolving in salt water into metabolizable compounds. Cheng et al. show that salt bridging between sodium hexametaphosphate or sulfated polysaccharides and guanidinium sulfates expels sodium sulfate to create a cross-linked network that is stable until the electrolytes are added back. The dried material is a moldable and recyclable thermoplastic that can be water stabilized with hydrophobic coatings. —Phil Szuromi
Abstract
Plastics that can metabolize in oceans are highly sought for a sustainable future. In this work, we report the noncovalent synthesis of unprecedented plastics that are mechanically strong yet metabolizable under biologically relevant conditions owing to their dissociative nature with electrolytes. Salt-bridging sodium hexametaphosphate with di- or tritopic guanidinium sulfate in water forms a cross-linked supramolecular network, which is stable unless electrolytes are resupplied. This unusual stability is caused by a liquid-liquid phase separation that expels sodium sulfate, generated upon salt bridging, into a water-rich phase. Drying the remaining condensed liquid phase yields glassy plastics that are thermally reshapable, such as thermoplastics, and usable even in aqueous media with hydrophobic parylene C coating. This approach can be extended to polysaccharide-based supramolecular plastics that are applicable for three-dimensional printing.