Bye bye microplastics new plastic is ocean degradable and recyclable
by Riko Seibo
Tokyo, Japan (SPX) Nov 22, 2024

Researchers at the RIKEN Center for Emergent Matter Science (CEMS), led by Takuzo Aida, have introduced a novel plastic that offers durability and biodegradability while addressing a pressing global concern - microplastic pollution in oceans. Unlike conventional materials, this innovative plastic dissolves in seawater, providing a sustainable solution for reducing microplastics in marine ecosystems, soils, and food chains. Their findings were published on November 22 in 'Science'.

Traditional plastics have long been recognized as a major environmental threat due to their non-biodegradability and accumulation in ecosystems. Although some biodegradable options, such as PLA, exist, their resistance to seawater degradation allows microplastic formation, harming marine life and infiltrating human food systems.

Aida's team tackled this issue by engineering supramolecular plastics - polymers bound by reversible interactions. The plastic's structure is created by combining two ionic monomers, forming robust salt bridges that provide strength and flexibility. One of the monomers, sodium hexametaphosphate, is a food additive, while the other is a guanidinium ion-based compound. Both can be metabolized by bacteria, ensuring environmental biodegradability.

"While the reversible nature of the bonds in supramolecular plastics have been thought to make them weak and unstable," said Aida, "our new materials are just the opposite." The researchers achieved stability through selectively irreversible cross-links in salt bridges, activated only in the presence of seawater electrolytes.

The production process revealed that desalting - a step involving separating structural salt bridges from free salt ions - was crucial for achieving durability. Without desalting, the dried plastic became brittle and unusable. When exposed to seawater, the cross-links dissolved, breaking down the plastic within hours.

The material boasts several advantages, including non-toxicity, non-flammability, and adaptability for various applications. At temperatures above 120 C, it can be reshaped like conventional thermoplastics. By modifying the guanidinium sulfate composition, the team created plastics with different hardnesses and tensile strengths. Applications range from durable, scratch-resistant materials to flexible, silicone-like options, as well as ocean-degradable plastics suitable for medical and 3D printing uses.

Recycling tests showed promising results, recovering 91% of hexametaphosphate and 82% of guanidinium from dissolved plastics. Biodegradation trials revealed that plastic sheets disintegrated in soil within 10 days, enriching it with phosphorus and nitrogen nutrients.

"With this new material, we have created a new family of plastics that are strong, stable, recyclable, can serve multiple functions, and importantly, do not generate microplastics," Aida emphasized.

Research Report:Mechanically strong yet metabolizable supramolecular plastics by desalting upon phase separation

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