Oxidative polymerization of acrylamide in the presence of thioglycolic acid

Abstract

Chemical polymerization of acrylamide at room temperature was examined by using thioglycolic acid-cerium (IV) sulfate and thioglycolic acid-KMnO 4 redox systems in acid aqueous medium. Water soluble polyacrylamides containing thioglycolic acid end groups were synthesized. The effects of the molar ratio of acrylamide to Ce(IV) n AAm /n Ce(IV ) , the polymerization time, the temperature, the monomer concentration, the molar ratio of cerium (IV) sulfate to thioglycolic acid and the concentration of sulfuric acid on the yield and molecular weight of polymer were investigated. Lower molar ratios 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 to 70 • C resulted in a decrease in the yield but generally resulted in a constant value for the molecular weight of polymer. With increasing polymerization time, the yield and molecular weight of polymer did not change substantially. 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 bound to polymer was investigated by UV-visible spectrophotometry and fluorescence measurements. The amount of Mn(II) incorporated into the polymer was determined using graphite furnace atomic absorption spectrometry. The mechanism of this phenomenon is discussed.

Synthesis and characterization of polyacrylamides containing meso‐2,3‐dimercaptosuccinic acid end groups

“…21,25,37,38 Because of low S H bonding energy, the formation of free radicals in reaction I in Scheme 1 is more likely than other reactions to initiate polymerization of AAm. It was reported that the formation of free radicals on carboxyl groups might be possible.…”

Swelling properties of acrylamide-N,N’-methylene bis(acrylamide) hydrogels synthesized by using meso-2,3-dimercaptosuccinic acid-cerium(IV) redox couple

“…These parameters are: the molar ratios of acrylamide/ cerium(IV) sulfate (n AAm /n Ce(IV) = 100 and 200) at constant crosslinker and acid concentrations, the concentration of sulfuric acid (C H 2 SO 4 = 0.0125 and 0.025 mol/l) at the n AAm /n MBAA = 40 and the molar ratios of acrylamide to N,N′-methylene bis(acrylamide) for different acid and initiator concentrations. The radical generation in the redox reaction of meso-2,3-dimercaptosuccinic acid and cerium(IV) sulfate in acid-aqueous medium is supposed to occur by one electron transfer from meso-2,3-dimercaptosuccinic acid to Ce(IV) according to the reactions given in Figure 1 as reported in the literature [18][19][20][21][22]. Because of low S-H bonding energy, the formation of free radicals in reaction I in Figure 1 is more likely than other reactions to initiate crosslinking polymerization of acrylamide and N,N′methylene bis(acrylamide) and oxidative termination of polymer radicals is also possible by ceric ions [18,20,21].…”

“…The radical generation in the redox reaction of meso-2,3-dimercaptosuccinic acid and cerium(IV) sulfate in acid-aqueous medium is supposed to occur by one electron transfer from meso-2,3-dimercaptosuccinic acid to Ce(IV) according to the reactions given in Figure 1 as reported in the literature [18][19][20][21][22]. Because of low S-H bonding energy, the formation of free radicals in reaction I in Figure 1 is more likely than other reactions to initiate crosslinking polymerization of acrylamide and N,N′methylene bis(acrylamide) and oxidative termination of polymer radicals is also possible by ceric ions [18,20,21]. In previous investigations, it is described that the formation of radicals on carboxyl groups may be possible [18][19][20][21][22].…”

“…Because of low S-H bonding energy, the formation of free radicals in reaction I in Figure 1 is more likely than other reactions to initiate crosslinking polymerization of acrylamide and N,N′methylene bis(acrylamide) and oxidative termination of polymer radicals is also possible by ceric ions [18,20,21]. In previous investigations, it is described that the formation of radicals on carboxyl groups may be possible [18][19][20][21][22]. However, the radical formation on carboxyl groups may appear less than that of the other radical formation reactions given in Figure 1, as the formation of free radicals on carcoxyl groups requires more energy.…”

“…However, ceric saltorganic reducing agent containing thiol functional group or groups are also new sources to initiate copolymerization of vinyl monomers at low tem-peratures. When reducing agent with thiol functional group is used in redox system of ceric saltorganic reducing agent, the formation of -S. radical is energetically most favorable due to low S-H bonding energy to initiate copolymerization of gel particles in acid-aqueous medium at lower temperatures [18][19][20][21][22][23]. The swelling of polymeric networks is influenced by the composition of the polymer i.e.…”