Synthesis, characterization, and thermal degradation kinetics of biuret–formaldehyde polymeric ligand and its polymer metal complexes

Abstract

In the present study, biuret–formaldehyde (BF) polymeric ligand was prepared by condensation reaction, and its polymer metal complexes [BF-M(II)] were prepared with transition metal ions. Synthesized polymers were characterized by elemental, spectral, and thermal analyses. The geometry of central metal ions was determined using magnetic susceptibility measurement and electronic spectra, which reveals that Co(II) and Ni(II) ions have octahedral geometry, while Cu(II) and Zn(II) ions have square planer and tetrahedral geometry, respectively. Thermogravimetric (TG) analysis was used to estimate thermal and kinetic behavior of polymers at heating rates of 10, 15, and 20 °C min−1 under helium atmosphere. The TG curves of polymers at three heating rates were more or less in similar shape, which indicated that mass loss is independent of heating rate. Thermogravimetric data were analyzed by means of model-free isoconversional method of Flynn–Wall–Ozawa and Kissinger–Akahira–Sunose on the whole range of temperature. It was found that values of apparent activation energy (E a) of [BF-M(II)] polymers are higher than BF and influenced by the metal type.