Upcycling Waste Polycarbonate to Poly(carbonate imine) Vitrimers with High Thermal Properties and Unprecedented Hydrolytic Stability

Abstract

The global market for polycarbonate (PC) increases steadily because of its heat resistance, toughness, and optical transparency. To achieve sustainability, the waste polycarbonate (WPC) should be recycled. This work reports a 100% atom-efficiency upcycling of WPC to a WPC-derived aldehyde (WPC-CHO). Then, poly(carbonate imine) vitrimers (PCIs) based on the WPC-CHO and two aromatic diamines were prepared. Generally, polyimines can cleave in mild acidic conditions such as 0.1 M HCl(aq) and seldom show good thermal and tensile properties. The PCIs in this work showed good thermal and tensile properties and an unprecedented resistance toward acid hydrolysis. They can survive even immersing in a 5 M H2SO4 THF/H2O solution for 6 months. This unusual resistance toward acid hydrolysis expands the application of PCIs in an acidic environment. Small pieces of PCIs can be compression-molded into a newly formed polymer film at 240 °C. This thermal reprocessability demonstrates the vitrimer characteristic of the PCIs. The PCIs can be degraded through simultaneous aminolysis of carbonate and transimination of imine by hexylamine (HA) in a catalyst-free mild condition. Based on the aminolysis and transimination, we degraded the cross-linking network in the PCI-based carbon fiber-reinforced polymer (CFRP) and recovered undamaged carbon fiber. This environmentally friendly work will attract the attention of researchers who are interested in sustainability and circularity.