Synthesis of Mg-Al Alkoxide/Ionic Liquid Particles as Heterogeneous Catalysts for Ring-Opening Polymerization of...

The widespread use of biodegradable plastics, especially polyesters, in biomedicine, packaging, and agriculture requires the investigation of efficient heterogeneous catalysts that are nontoxic and easily recyclable. Herein, we report solvolytic and solvothermal methods to synthesize bimetallic Mg-Al alkoxides (BMA) and their subsequent modifications using the phosphonium-based ionic liquid trihexyltetradecylphosphonium bis-(2,4,4-trimethylpentyl)-phosphinate (IL-PO₂). The successfully modified Mg-Al alkoxide/ionic liquid particles were explored as a heterogeneous initiating/catalyzing system for the ring-opening polymerization (ROP) of ε-caprolactone. Morphological and structural studies were conducted in order to explore the properties in detail and to better understand the differences from layered double hydroxides modified with IL-PO₂, which had already been applied to ROP. The thermal stability was confirmed up to 170 °C, i.e., sufficient for ROP. The water content was also determined by thermogravimetric analysis, and it was found that water is present as surface water and is incorporated into the structure. The explanation for the very good catalytic activity was possible after a model reaction with a higher concentration of catalysts, 10% for BMA-2-IL-PO₂, which confirmed that IL-PO₂ also actively participates in ROP.