Optimization and Mechanistic Insights of Zinc Ascorbate Catalyst for Ring‐Opening Polymerization of Caprolactone Using <scp>RSM</scp> Methodology and <scp>DFT</scp> Calculations

ABSTRACT Polycaprolactone (PCL) is an aliphatic polyester recognized for its exceptional versatility and biodegradability, which has garnered significant attention for a wide range of applications. This study presents an innovative methodology for the synthesis of PCL through the ring‐opening polymerization (ROP) of ε‐caprolactone (CL). The approach employs a biocompatible and environmentally benign organometallic zinc ascorbate complex as a catalyst. Derived from ascorbic acid, a well‐established reducing agent, zinc ascorbate serves as a sustainable alternative to conventional tin‐based catalysts, thereby mitigating environmental impact and enhancing safety measures. The catalyst operates effectively under solvent‐free conditions and does not require initiators, achieving a high polymer conversion rate of approximately 79%. The optimization of the reaction parameters was conducted using response surface methodology (RSM) employing a central composite design (CCD). The structural and chemical characterization of the catalyst as well as the resulting polymers was performed using proton nuclear magnetic resonance ( 1 H NMR), Fourier‐transform infrared spectroscopy (FTIR), and x‐ray diffraction (XRD) analyses. Additionally, density functional theory (DFT) calculations elucidated a four‐step coordination‐insertion mechanism for the polymerization of cyclic lactones, with findings supported by Gibbs free energy, electrostatic potential, and non‐covalent interactions. This study underscores the potential of zinc ascorbate as a reliable, nontoxic, and cost‐effective catalyst, fulfilling the increasing demand for sustainable and efficient polymerization processes in commercial and biomedical applications.