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

Poly(butylene adipate-<i>co</i>-terephthalate)\n(PBAT)\nis a thermoplastic biodegradable polyester with broad market prospects\ndue to its desirable toughness, ductility, and water resistance. However,\ncompared with traditional plastics, its insufficient mechanical strength\nlimited its scope of applications. Herein, inspired by the reinforcement\nconcept of polyurethane and leveraging the rich presence of aromatic\nrings in the PBAT molecular chain, we incorporated cation–π\nand hydrogen-bonding interactions into PBAT chains to enhance the\nmechanical properties. Cationic quaternary ammonium (QA) groups were\ncoupled into the mainchain generating PBATQA copolyester through an\nisocyanate chain extension reaction, and the effects of QA content\non crystallinity, mechanical properties, and melt rheology were investigated.\nThe synergistic occurrence of hydrogen-bonding and cation–π\ninteractions was demonstrated by DFT calculation. At a low QA content\nof 1.7 wt %, we achieved a significantly enhanced tensile strength\nof 44.2 MPa and an elongation at break of 1498%. In addition, due\nto the broad melting range and the relatively high modulus around\nmelting transition temperature, the synthesized PBATQA can be easily\nprocessed into complicated objects via 3D printing and implementation\nof complex shape memory processes.