Synthesis of Polyisoxzolidines As Potential Corrosion Inhibitors

Abstract

Several polyisoxazolidines, a new class of polymers, were synthesized using 1,3-dipolar cycloaddition reaction of some alkene-nitrones, and cocycloaddition of dialkene and dinitrones. Hydroxylamine, N-(10-undecenyl)hydroxylamine and aldehyde, p-allyloxybenzaldehyde and p-10-undecen-1-yloxybenzaldehyde were employed to synthesize the alkene-nitrone monomers. The dialkene, p-diallyloxybenzene, and dinitrones, N,N'-dimethyl- p-phenylenedinitrone and N,N'-dimethyl-1,5-pentylidenedinitrone were used to synthesize the polyisoxazolidines via cocycloadditions. IR, 1H, and 13C NMR spectroscopy were used to characterize the various synthesized monomers as well as the polymers. The kinetics of the polymerization processes was investigated by 1H NMR spectroscopy. Kinetic data is helpful in controlling the molar mass of the polymers. End group analysis by 1H NMR spectroscopy was used to determine the average molar mass of the polymers. In order to stabilize the molecular mass of the polymers, the end group of the living polymers was capped by reacting with monofunctional reactive alkene, like methyl acrylate. The synthesized polyisoxazolidines, containing multiple donor atoms (N, O), quaternary ammonium group, π-electrons, and electron-rich aromatic group, were used to study their efficiencies on the corrosion inhibition of mild steel in acidic solutions (1 M HCl and 0.5 M H2SO4) at 60 °C using gravimetric and electrochemical methods. Most of the compounds have shown very good corrosion inhibition efficiency (IE%) in HCl solution as measured by the gravimetric method. Comparable results were obtained by the electrochemical method using Tafel plots for the inhibition efficiency of some of the selected synthesized compounds. It is evident from the Tafel plots that in most of the compounds the inhibitor adsorption shifted the corrosion potential (Ecorr), in the negative direction with reference to the blank in 1 M HCl, signifying that suppression of the cathodic reaction is the main effect of these corrosion inhibitors.