Catalyst-free polyesterification enables the formation of multifunctional and sustainable polyesters

Abstract

Aliphatic polyesters show potential as substitutes for non-biodegradable materials, helping reduce plastic pollution. However, their synthesis often requires heavy metal catalysts, and conventional polyesters lack property diversity, limiting broader applications. Here, we developed an environment-friendly, multifunctional polyester as a versatile material. Cationic aggregation-mediated multifunctional polyesters have been effectively synthesized through a large-scale melt polycondensation process utilizing a carboxyl back-biting mechanism in the absence of any catalyst. Cationic aggregation in situ acts as a dynamic cross-linking point, enabling a single polymer to exhibit switchable and contrasting properties, transitioning between elasticity, transparency, and water-solubility and rigidity, opacity, and water-insolubility. Meanwhile, the material shows outstanding weldability at room temperature after fracture, and the welded material exhibits mechanical properties similar to the original material due to dynamic cross-linking points. The material exhibits a significantly higher degradation rate compared to traditional polyester, even under seawater conditions. Moreover, the polyester's switchable water solubility allows efficient separation from mixed plastics for closed-loop recycling. Additionally, replacing with antibacterial cations can upcycle the polyester into high-value antibacterial materials, enhancing sustainability. This work provides insights into the design of multifunctional, catalyst-free and sustainable polyesters for a broad range of applications.