Design of Weldable and Recyclable Fluorine-containing Adhesives Utilizing Dynamic-covalent Boroxine Bonds

The advancement of functional adhesives featuring recyclable and repairable properties is of great significance in interfacial science and engineering. Herein, a series of high-strength, recyclable fluorine-containing adhesives (ESO x -FPF) were designed and synthesized by crosslinking two prepolymers, FPF-B (derived from side-chain fluorinated diol, isocyanate, and aminoboric acid) and ESO-B (synthesized from biobased epoxy soybean oil and aminoboric acid), through dynamic boro-oxygen bonds. The resulting adhesive exhibited an optimal tensile strength of 42 MPa and the shear strength on steel plates reached as high as 3.89 MPa. More importantly, benefiting from the dynamic reversibility of the boron-oxygen bonds along with the hydrogen bonds interaction, ESO x -FPF can be welded with the assistance of solvents and recycled for multiple cycles. The outstanding healing efficiency and excellent reprocessability of these functional adhesives were confirmed by mechanical testing. Moreover, the as-prepared adhesives demonstrated universal and remarkable adhesion to various substrates, such as aromatic polyamide, aluminum plates and polycarbonate, meanwhile, they could be easily disassembled and recycled using ethanol without damaging the substrates surface. This study not only provides a simple strategy for the synthesis of eco-friendly adhesives with weldable and recyclable properties, but also sheds light on the development of other functional materials utilizing dynamic covalent chemistry.