Mechanically Robust and Chemically Recyclable Poly(β-Amino Esters)-Based Thermosetting Plastics

The development of chemically recyclable thermosetting plastics using dynamic covalent bonds is of great importance in the construction of a sustainable society. However, there remains a bottleneck barrier in fabricating dynamic covalent thermosetting plastics with simultaneously high mechanical strength, thermal and dimensional stability, and room-temperature chemical recyclability. Herein, a series of poly(β-amino esters) (PBAEs)-based thermosetting plastics with high mechanical strength, desirable dimensional stability, and room-temperature chemical recyclability were fabricated through the aza-Michael addition reaction of bisphenol A glycerolate diacrylate (BG), poly(propylene glycol) bis(2-aminopropyl ether) (PPG), and adipic acid dihydrazide (ADH). By increasing the molar ratios of ADH, the mechanical properties of PBAE-based thermosetting plastics can be scientifically enhanced via the increase of the cross-linking densities and hydrogen bond contents in the polymer networks. Typically, the tensile strength and Young’s modulus of PBAE5 can be improved to 4.5 and 10.6 times of PBAE1, respectively. Meanwhile, based on the rigid polymer network structures, PBAE-based thermosetting plastics exhibited very small creep strain at evaluated temperatures. More importantly, PBAEs-based thermosetting plastics can be easily depolymerized into value-added monomers in an alkaline aqueous solution at room temperature through the hydrolysis of β-amino esters. Therefore, systematically tailoring the cross-linking density and hydrogen bond contents of the polymer network is an efficient and feasible strategy to construct mechanically strong and dimensional stable dynamic covalent thermosetting plastics with room-temperature chemical recyclability.