The Reversible Discoloration Reaction of Polyvinylalcohol Aqueous Solution by pH

Abstract

The aqueous solution of the polyvinyl alcohol (PVA-I) derived by alkaline methanolysis of polyvinyl acetate polymerized in the presence of aldehyde showed a reversible color change with the change of pH, yellow brown in alkaline and colorless in acidic state.
However, the polyvinyl alcohol (PVA-II) derived from polyvinyl acetate polymerized in the presence of acetone was colorless, even in alkaline state.
Spectroscopic study was carried out about PVA-I, PVA-II, and 2, 4-hexadienal. From the resemblance of spectroscopic behavior between PVP-I and 2, 4-hexadienal, it was considered that the course of color change of PVA-I was due to the tautomeric keto-enol isomerization of terminal carbonyl group.