Analysis of the Bis(benzoylacetonato)zirconium(IV) Chloride Complex Compound Mulliken Charge Used As a Catalyst in the Ring Opening Polymerization of ε-Caprolactone

Abstract— Poly(ε-caprolactone) (PCL) is one of the promising polymers because it can be utilized as a substitute for petroleum-based polymers that are difficult to biodegrade in nature. PCL has non-toxic properties, high crystallinity, and biodegradable. Therefore, this polymer is widely used for medical purposes and environmentally friendly packaging. The purpose of this study was to compare the degree of polymerization, catalytic activity and thermal properties between PCL produced using bis(benzoylacetonato)zirconium(IV) catalyst (2a) with the PCL produced using other bis(β-diketonato)zirconium(IV) chloride catalyst (2b, 2c). In this research, ring opening polymerization (ROP) of ε-caprolactone (ε-CL) was performed by using complex 2a as a catalyst. The polymerization reaction lasts for 4 h at 100°C. The results of the research showed that ε-CL was successfully polymerized as proven in the results of its characterization. The molecular structure of the obtained PCL was analyzed by using FTIR, ¹H NMR, ¹³C NMR, XRD, DSC, and TGA. The PCL produced in this study was a semicrystalline polymer. Meanwhile, a Mulliken charge of zirconium central atom in complex 2a–2c was also measured. In Mulliken charge analysis, the Mulliken charge of complex 2c has the highest Lewis acidity in comparison with complex 2a and 2b.