Butler’s cyclopolymerizaton protocol in the synthesis of diallylamine salts/sulfur dioxide alternate polymers containing amino acid residues

In solvent acetone, ethyl ester hydrochloride of N,N-diallylmethionine I having sulfide motifs underwent alternate cyclopolymerization with SO₂ to give copolymer II (i.e. I-alt-SO₂), while in DMSO (Me₂S = O), it gave terpolymer III containing sulfide and sulfoxide motifs in a 1:1 ratio as a result of oxygen transfer from Me₂SO. Remaining sulfide group in III upon oxidation with H₂O₂ afforded polymer sulfoxide IV and polymer sulfone V. Likewise; copolymerization of hydrochloride salt of N,N-diallylmethionine VI with SO₂ in DMSO gave copolymer VII containing sulfide/sulfoxide motifs in a ≈ 1:1 ratio. VII was oxidized to polymer sulfoxide VIII. The chemical and physical properties of these polymers were determined by FT-IR, NMR, TGA and surface tension. The solution properties of these polymers were studied in detail. The critical micelle concentration of the polymers was determined to be ≈ 7 ppm. The presence of polymers III, IV, V, VII and VIII at a very low concentration of ≈ 6 ppm in 1 M HCl imparted superb inhibitions of mild steel corrosion of 89, 94, 87, 96, and 94%, respectively.