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Polymerization Of Acrylamide Initiated With 3-Mercaptopropionic Acid-Ce(Iv) Redox System And Synthesis Of Acrylamide Gels

Polymerization of acrylamide monomer was performed at low temperatures using 3-mercaptopropionic acid-cerium(IV) sulfate and 3-mercaptopropionic acid-KMnO4 and redox systems in acid aqueous medium. Water soluble polyacrylamides containing 3-Mercaptopropionic acid end groups were synthesized. Moreover by using 3-Mercaptopropionic acid-Ce(IV) redox system, insoluble copolymers of acrylamide-methylene bis(acrylamide) in water were synthesized.

The effects of mole ratio of acrylamide to initiator (n_MPA= n_Ce(IV)), polymerization time, temperature, and concentration of sulfuric acid on the yield and molecular weight of polymer were investigated. Swelling properties of gels obtained in copolymerization reactions, depending on initior concentration, acid concentration and the amount of methylene bis(acrylamide) at constant acid concentration were examined.

The decrease in the mole ratio of acrylamide/Ce(IV) at constant monomer concentration resulted in an increase in the yield but a decrease in molecular weight of polymer. The increase of reaction temperature from 20 ^oC to 70 ^oC resulted in a decrease in the yield but indicated generally a constant value for the molecular weight of polymer. With increasing of polymerization time, the yield and molecular weight of polymer did not change considerably.

Swelling equilibruim ratios decreased with a decrease in the molar ratios of acrylamide/Ce(IV) and acrylamide / NMBA. It was observed that the hydrogels synthesized at lower acid concentration absorbed more water.

Ce(IV) and Mn(VII) ions are reduced to Ce(III) and Mn(II) ions, respectively in the polymerization reaction. The existence of Ce(III) ion bonded to polymer was investigated by UV-visible spectrometry and fluorescence measurements. The amount of Mn(II) that is incorporated to the polymer was determined using graphite furnace atomic absorption spectrometry. The mechanism of this phenomenon is discussed.