The study, published in *Chem*, demonstrates how incorporating movable crosslinks in polymers can strengthen materials without compromising their degradability. Traditionally, enhancing polymer durability has come at the cost of biodegradability, as stronger polymers tend to resist breakdown. The Osaka University team solved this issue by integrating movable ring-shaped crosslinks known as cyclodextrins, which enhance both strength and degradability.
Cyclodextrins, threaded on one polymer strand and attached to another, act as crosslinkers that increase the plastic's toughness. "Our polymer design using movable cyclodextrin crosslinks increased polymer toughness by over eight times," said lead author Jiaxiong Liu. "Stiffness, ductility, fracture stress, and fracture strain all improved because the cyclodextrin groups effectively dispersed local stress."
In addition to bolstering strength, the cyclodextrin crosslinks make the polymers easier to break down during enzymatic treatment by creating more space within the polymer network, giving enzymes easier access to cleavage sites. "The polymers were readily degraded by Novozym 435, an enzyme that specifically attacks the ester bonds of the polymer backbone," explained senior author Yoshinori Takashima. "The presence of the bulky cyclodextrin crosslink groups decreased entanglement and aggregation of the polymer chains, which facilitated the access of the enzyme to the ester bonds for cleavage." This design improvement boosted biodegradability by twenty times over polymers without cyclodextrin crosslinks.
These advanced biodegradable plastics not only break down readily into useful precursor molecules for future materials but also contribute to a more sustainable society by reducing waste and promoting resource recycling.
Research Report:Exploring Enzymatic Degradation, Reinforcement, Recycling and Upcycling of Poly(ester)s-Poly(urethane) with Movable Crosslinks
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