Poly(butylene adipate-<i>co</i>-terephthalate)-Quaternary Ammonium Copolyester with Highly Enhanced Mechanical Performance through Synergistic Cation–π and Hydrogen-Bonding Interactions

Poly(butylene adipate-co-terephthalate) (PBAT) is a thermoplastic biodegradable polyester with broad market prospects due to its desirable toughness, ductility, and water resistance. However, compared with traditional plastics, its insufficient mechanical strength limited its scope of applications. Herein, inspired by the reinforcement concept of polyurethane and leveraging the rich presence of aromatic rings in the PBAT molecular chain, we incorporated cation–π and hydrogen-bonding interactions into PBAT chains to enhance the mechanical properties. Cationic quaternary ammonium (QA) groups were coupled into the mainchain generating PBATQA copolyester through an isocyanate chain extension reaction, and the effects of QA content on crystallinity, mechanical properties, and melt rheology were investigated. The synergistic occurrence of hydrogen-bonding and cation–π interactions was demonstrated by DFT calculation. At a low QA content of 1.7 wt %, we achieved a significantly enhanced tensile strength of 44.2 MPa and an elongation at break of 1498%. In addition, due to the broad melting range and the relatively high modulus around melting transition temperature, the synthesized PBATQA can be easily processed into complicated objects via 3D printing and implementation of complex shape memory processes.