Transparent, Self-Healing, and Recyclable Biomass-Based Covalent Adaptable Networks Formed via Magnolol and Dynamic Boronate Ester

Introducing renewable compounds and dynamic covalent bonds into polymeric networks to achieve sustainability, self-healing, and reprocessability is of great significance in reducing the carbon footprint of polymeric materials. This study developed sustainable biomass covalent adaptable networks (BCANs) using renewable magnolol and dynamic phenylborate. First, a prepolymer was obtained by using the phenolic hydroxyl group on magnolol and diglycidyl ether for epoxy ring opening addition polymerization. Then, the allyl group of magnolol was used to perform a thiol-ene photochemical reaction with a dithiol containing boronic ester; ultimately, magnolol-based sustainable BCANs were prepared. The dynamically reversible boron ester bonds in the networks enable both the recyclability and self-healing properties, enhancing their application scope in different scenarios. Additionally, the study confirms that after undergoing four man-made damages, the BCANs' self-healing capability remained almost unchanged, and even the Young's modulus showed improvement. These BCANs demonstrate significant potential in sustainability by featuring monomer renewability, self-healing, and recyclability, characteristics that are critically valuable in replacing petroleum-based thermosets.