Renewable benzoxazine-based thermosets from cashew nut: Investigating the self-healing, shape memory, recyclability and antibacterial activity

The preparation of sustainable bio-based polybenzoxazines with multifuctional applications is highly desirable but still challenging. Here, we propose a facile strategy to address this dilemma by introducing dioxaborolane bonds into the benzoxazine network. Renewable dynamic cardanol-based polybenzoxazine networks were prepared using the renewable waste material, cardanol (a byproduct of cashew nut processing), as the starting material and fabricated by incorporating dioxaborolane bonds. The dioxaborolane-containing cardanol-based benzoxazine thermosets (PCBOz-DBs) showed excellent reprocessability, self-healing property, shape memory behavior, and antibacterial activity. PCBOz-DBs have a controllable mechanical strength in a wide range between stretchability (elongation at break: over 587%) and stiffness (tensile strength: 5.88 MPa), as well as an excellent shape memory performance, by tailoring dioxaborolane bond content without catalyst. The polymer has a strong tissue-adhesive property and can firmly adhere to a variety of substrates, such as metal, plastic, and glass. PCBOz-DBs showed inhibition rates of 95.61% and 99.98% against Escherichia coli and Staphylococcus aureus, respectively. Moreover, the distinct network makes PCBOz-DB recyclable over multiple times without compromising its property, showing significant and self-healing properties under relatively low temperature (100 °C) and short healing time (5 min). The prepared PCBOz-DB, which is reusable, recyclable, and renewable, can achieve the goal of cleaner production by using bio-renewable biomass and reducing petrochemical resources, production, and energy emissions.