Open-loop recycling of post-consumer PET to closed-loop chemically recyclable high-performance polyimines

Intriguing high-performance polyimines (PI) were designed from diamines recovered by open-loop recycling of postconsumer PET bottles by microwave-assisted aminolysis. These new PIs had excellent thermal properties (Tm = 226–286 °C, Tg = 88–148 °C, heat resistance up to 327 °C) and super-high toughness and strength with Young's modulus of 4.02–4.93 GPa and tensile strength of 237–467 MPa, both significantly higher compared with common engineering plastics. The synthesized PIs also demonstrated recyclability “on demand” to original building blocks via mild and ultrafast acetic acid catalysed hydrolysis (70 °C for 10 min). Furthermore, the recovered monomer mixture was directly repolymerizable providing attractive closed-loop polymer-to-polymer recyclability under extremely mild conditions. These high performance thermoplastics, with easily tunable properties by selection of diamine used for aminolysis, in combination with closed-loop chemical recyclability have great promise as next-generation circular materials, designed from recycled plastics waste, for a wide property and application range.