Polymerization initiated by the redox system hydrogensulfite/oxygen, 1. Polymerization of acrylic acid

Abstract

The polymerization of acrylic acid in water by the redox initiation system hydrogensulfite/ oxygen was found to proceed fast to give oligomers in high yield, in spite of introducing a large amount of oxygen known as a strong radical inhibitor. In the polymerization system, the concentration of oxygen was kept at a very low level on account of the rapid reaction of hydrogensulfite with oxygen. At high concentration of hydrogensulfite, both hydrogensulfite oxidation rate (Rex) and polymerization rate (R,) vary with the flow rate of air. R , is proportional to the square root of R,, suggesting that the termination is a bimolecular reaction, a radical intermediate formed from hydrogensulfite oxidation being the initiator of this polymerization system. Hydrogen was found to behave as a chain transfer agent, and its chain transfer constant is 0,15 at pH 6,9 and 25 "C.