Dynamically Cross-Linking Soybean Oil and Low-Molecular-Weight Polylactic Acid toward Mechanically Robust, Degradable, and Recyclable Supramolecular Plastics

To promote the sustainable development of society, it is important to develop methods for facile fabrication of bio-based plastics that are mechanically robust and capable of recycling and completely degrading in soil. In this study, such bio-based supramolecular plastics are conveniently and cost-effectively fabricated by cross-linking epoxidized soybean oil (ESO) and low-molecular-weight polylactic acid (PLA) (approximate to 2 kDa) with dynamic boroxines. The bio-based supramolecular plastic, which is denoted as ESO-PLA, exhibits a tensile strength of approximate to 43 MPa and is highly flexible and water-resistant. After being stored in an environment with a 100% relative humidity for 10 days, the tensile strength of the plastic remains higher than polyethylene. Due to the reversibility of boroxines, the ESO-PLA plastic can be conveniently processed into different shapes and products. Meanwhile, the plastic can be recycled multiple times for repeated usage by either hot-pressing or solvent-assisted depolymerization/repolymerization methods. Benefiting from the easy degradation of ESO and low-molecular-weight PLA, the breakage of boroxine cross-links enables rapid and complete degradation of the plastics in soil within 60 days. Additionally, in vitro and in vivo tests prove that the ESO-PLA plastic exhibits satisfactory biocompatibility, which extends its application in medicine, food, and cosmetics industries.