A Tough Physical Bond-Based Gel that is Fully Aligned to the Circular Economy

Synthetic materials play a crucial role in many facets of modern society owing to their outstanding durability, cost-effectiveness, and adaptability allowing them to be engineered into a diverse array of applications. Despite their advantages, synthetic materials follow the take-make-dispose linear economy model which is unsustainable. The circular economy is an alternative model that seeks to reduce waste by keeping resources in a loop as long as possible through processes such as material design, green processing, repairing, recycling, and biodegradation. However, achieving full alignment with the principles of the circular economy remains elusive and the usual problem stems from not choosing the correct starting raw material. One solution is to use bioderived raw materials that are inherently biodegradable. When biodegraded, their decomposition products can be used as building blocks for the subsequent generation of raw materials, thereby perpetuating a sustainable cycle. Nevertheless, bioderived raw materials like alginate and cellulose are often mechanically weak or stiff by themselves which limits their widespread applicability. The challenge is whether we could develop a tough yet sustainable material that is fully aligned with the circular economy.<br/><br/>Herein, we developed a tough physical bond-based gel that is fully aligned with the circular economy. The material comprises a polymeric backbone with other organic compounds all of which are bioderived. We confirmed that the components interact with each other via strong physical bonds like hydrogen bonds, ionic interactions, and ion-dipole interactions. The material is tough as it can dissipate energy through the breakage of reversible physical bonds and the rearrangement of the components, delaying the rupturing of the polymer network. When contrasted against natural polymers reinforced by conventional toughening strategies such as double network and metal coordination, our gel exhibits superior toughness of at least one order of magnitude higher. Our material can achieve 100% self-healing efficiency and is close to 100% transmittance over the entire visible spectrum. Furthermore, it can biodegrade fully in soil in 5 days and is highly biocompatible and recyclable. This opens avenues to apply tough yet sustainable materials in food science, biomedical, and green robotics applications.