Fully Closed-Loop Recyclable Thermosetting Shape Memory Polyimide

Recycling is a major approach in developing sustainable polymers to cope with environmental pollution and resource waste, but it still remains a challenge to design high-performance closed-loop recyclable shape memory polyimide. Here, we report a type of fully recyclable thermosetting shape memory polyimide (RPI) containing a reversible dynamic imine-cross-linked network formed via polycondensation between amine-terminated bisimide and 1,3,5-triformylbenzene in the absence of any catalyst. The cured RPI exhibits excellent mechanical properties with Young's modulus, breaking elongation ratio, and tensile strength of 1803 +/- 97 MPa, 10 +/- 2.3%, and 87.1 +/- 3.38 MPa, respectively. Moreover, the RPI features an excellent shape memory effect with a shape fixity ratio up to 96 +/- 1.1% and shape recovery ratio up to 97 +/- 0.32%. The controlled recycling experiments show that the obtained RPI can be fully closed-loop recycled with a strength recycling efficiency of 97%. The whole recycling process does not require additional metal catalysts or complicated hot-pressing processes, and the comprehensive performances of the reformed RPI are not compromised obviously. Owing to the high mechanical strength, thermostability, and excellent shape memory properties combined with recycling capabilities, the RPI is a promising multifunctional thermoset for sustainable engineering applications to avert environmental impact and resource waste.