The reaction of propane sultone with macromolecules. II. Poly(vinyl alcohol)

The sulfopropylation of poly(vinyl alcohol) (PVA) with propane sultone under different conditions has been studied. Attempts to carry out the reaction via the sodium alcoholate of PVA, prepared by different methods, failed, gave low yields or resulted in the formation of insoluble reaction products. The best way to obtain sulfopropyl poly(vinyl alcohol) (SPPVA) was to react propane sultone with PVA dissolved in dimethyl sulfoxide (DMSO) in the presence of potassium carbonate. Most probably the reaction occurs via dimethyl-(3-sulfopropoxy)sulfonium salt which is formed by reaction of propane sultone with DMSO. By passing a solution of the potassium salt of SPPVA through an acidified ion exchange column the free acid was obtained. Both the potassium salts and the free acids were hygroscopic, water-soluble substances showing typical polyelectrolyte properties.