Synthesis and structure design of novel unsaturated copolyesters based on indazole moiety in the main chain with good thermal stability for catalytic activity and anti-corrosion applications

Abstract

Novel unsaturated polyesters based on indazole moiety in the main chain are prepared by interfacial polycondensation of two different indazoline monomers with an acid chloride. The producing copolyesters were confirmed and described by different techniques including Fourier-transform infrared spectroscopy (FTIR), and proton nuclear magnetic resonance (1H-NMR). Their crystallinity and thermal stability are measured through X-ray powder (XRD) and thermogravimetric analysis (TGA) and show that they have good thermal stability which is affected by their crystallinity. The morphological features of the synthesized copolyesters were tested by scanning electron microscopy (SEM). Moreover, the resulting copolyesters were intended to be utilized as a catalyst in the preparation of polysubstituted imidazoles produced by three-component ammonium, and acetate 1,2-diketone with an aldehyde under mild conditions. The corrosion mitigation features of the fabricated unsaturated copolyesters as inhibitors for mild steel corrosion in molar hydrochloric acid were investigated. The unsaturated copolyesters exhibited respectable inhibition characteristics owing to robust adsorption on the metal interface and the construction of a defensive layer. The maximum protection capacity values ranged from 94.87 to 98.41% in the presence of 100 ppm of copolyesters. Adsorption of the unsaturated polyesters followed the Langmuir isotherm. Potentiodynamic polarization (PDP) examinations showed that the studied unsaturated polyesters were mixed-kind inhibitors.