Determination of HOMO and LUMO of bis(β-diketonate)zirconium(IV) compound used as a catalyst in the ring opening polymerization of ε-Caprolactone and δ-Valerolactone

Abstract

Poly(ε-caprolactone) (PCL) and poly(δ-valerolactone) (PVL) are aliphatic polyesters that can generally be used for basic medical materials such as bone and dental implant materials, drug delivery systems, and scaffolds in tissue engineering. PCL and PVL belong to the polylactone group which have superior properties such as good biocompatibility, nontoxicity, flexibility, thermoplastic and can be biodegraded in a controlled manner. These superior properties make it the main choice in producing medical materials. This study aims to determine the degree of polymerization of PCL and PVL catalyzed using a bis(β-diketonate)zirconium(IV) complex. In addition, analysis of the Highest Occupied Molecular Orbital (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO) was also carried out on the catalyst complex. The ring-opening polymerization reaction (ROP) of ε-caprolactone (ε-CL) and δ-valerolactone (δ-VL) lasted for 4 h at 100 °C. The resulting PCL and PVL were then characterized for their chemical and thermal properties using FTIR, 1HNMR, XRD, DTA and TGA. Both PCL and PVL are semicrystalline. On the other hand, the resulting PCL has a melting point of 65.5 °C, with a degree of polymerization (DP) of 17. Meanwhile, the resulting PVL has a melting point of 63.4 °C with a DP of 8.