Aqueous polymerization of acrylamide initiated by permanganate/oxalic acid redox system

Abstract

The polymerization of acrylamide initiated by permanganate/oxalic acid redox pair has been studied in aqueous media a t 35 & 0.2OC in nitrogen atmosphere.The rate of polymerization is independent of activator (oxalic acid) concentration (0.75.1Op3 to 7.5.10-3 mole/l.) except at very high (above 7.5.10-3 mole/l.) or very low (below O.75.lOW3 mole/l.) concentrations of the activator. The rate varies linearly a t low monomer Concentration. The catalyst exponent decreases from nearly unity to 0.65 with the increase in the concentration of catalyst (KMn04) probably due to participation of primary radicals in the termination of the growing chain.The initial rate increases with increase in the polymerization temperature. The overall energy of activation has been found to be 11.97 Kcal/mole within the temperature range 25-50 O C .Organic solvents (water miscible only) and salts (KCl, Na2S04) depress the initial rate but small amounts of manganous salts (MnS04) can increase the initial rate t o a considerable extent. High concentration of salts (Na2S04, KC1, and MnS04) causes termination of the growing chain. A complexing agent, NaF, decreases the initial rate but the limiting conversion is increased.Introduction of new catalyst a t intermediate stages of polymeiization increases both the rate and the limiting conversion. ZUSAMMENFASSUNG: Die durch das Redoxsystem Permanganat/Oxalsaure ausgeloste Polymerisation von Acrylamid wurde untersucht, und zwar unter Stickstoff in waariger Losung bei 35 & 0,ZoC. Die Polymerisationsgeschwindigkeit ist im Konzentrationsbereich von 0,75 a l O -3 bis 7,s .lO-3 moll1 von der Oxalsaurekonzentratiou unabhangig. Bei niedriger Monomerkonzentration ist die Reaktionsgeschwindigkeit dieser proportional. Der Exponent der Katalysatorkonzentration (KMn04) nimmt mit steigender Konzentration von nahezu 1 auf etwa 0,65 ab, vermutlich wegen eines zusatzlichen Abbruches wachsender Ketten durch Prim& radikale. Die Anfangsgeschwindigkeit nimmt mit steigeuder Polymerisationstemperatur zu. Zwischen 25 und 50 O C betriigt die Bruttoaktivierungsenergie 11,97 kcal/mol. Kleine Mengen an MnS04 steigern die Anfangsgeschwindigkeit betrachtlich, wogegen sie durch andere Salze (KCl, Na~S04) oder durch organische, mit Wasser mischbare Losungsmittel erniedrigt wird. Hohe Konzentrationen an NazS04, KC1 und auch MnS04 verursachen Kettenabbruch. NaF, das als Komplexbildner wirkt, vermindert die Anfangsgeschwindigkeit, wogegen es die Ausbeute steigert.Wird wahrend der Polymerisation in zeitlichen Abstlnden neuer Katalysator (KMn04) zugesetzt, dann steigt sowohl die Reaktionsgeschwindigkeit als auch die Ausbeute.

Effect of various medium on permanganate - lactic acid initiated polymerization of acrylamide

“…The addition of manganous sulphate to the system causes an increase in both the limiting conversion and the overall rate of polymerization. These observations are similar to those made by Misra et al (14)(15)(16) and differ slightly from the same group of workers (17) in that even at high concentration of manganous salt no decrease either in rate or limiting conversion is noticed. The disproportionation reaction occurring between Mn 4+ and Mn 2+ ions to generate Mn 3+ ions according to equation…”

“…It has been found that the free radical polymerization of various monomers like ionogenic (1)(2)(3)(4)(5)(6)(7) and the properties of the resulting polymers depend considerably on the nature of the medium. The use of water -organic solvents and watersalt mixtures give the possibility to vary the properties of the medium and to obtain the information about the influence of the medium on the polymerization (8)(9)(10).…”

The study of free radical polymerization of acrylonitrile by oxidation–reduction system using potassium persulfate–thiourea in aqueous medium

“…Besides its economical benefits, suppression of side reactions such as branching is an additional advantage over common thermal initiation methods. In this way, various redox systems have used successfully for the polymerization of organic vinyl monomers in aqueous media 8–21. A study of the kinetics of polymerization by thiourea and Ce(IV) have been studied 22, 23.…”

“…In this way, various redox systems have used successfully for the polymerization of organic vinyl monomers in aqueous media. [8][9][10][11][12][13][14][15][16][17][18][19][20][21] A study of the kinetics of polymerization by thiourea and Ce(IV) have been studied. 22,23 Various redox systems have used potassium persulfate (K 2 S 2 O 8 ) successfully for the polymerization of organic vinyl monomers in aqueous media.…”

Grafting vinyl monomers onto silk fibers. VIII. Graft copolymerization of methyl methacrylate onto silk using tetravalent manganese–oxalic acid redox system

“…Palit and c o -~o r k e r s~-~ and Mishra et al [5][6][7][8] have already exploited this field of research using permanganate ion as an initiator. This ion coupled with organic substrates acts as an efficient redox system for the initiation of vinyl polymerization.…”