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

Abstract

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.