Mechanism of the polymerization of acrylamide initiated by the glycerol/Ce(IV) redox system

Abstract

The mechanism of the polymerization of acrylamide in aqueous medium initiated by the glycerol (R)/Ce(IV) redox system was studied. The rate of monomer disappearance was found to be directly proportional to [MI3'', [Ce(IV)]"*, and R1'2 at lower concentrations of Ce(1V). The rate of the disappearance of ceric ions was found to be inversely proportional to [MI and directly proportional to [Ce(IV)] and [R]. Consistent with the findings of earlier investigations, a complex formation between monomer, acrylamide, and ceric ion is indicated. The experimental results show the termination to be mutual. On the basis of these and other kinetic results, an appropriate mechanism is proposed. At higher concentration of Ce(IV), a different mechanism seems to operate. The rates of disappearance of both the monomer and ceric ions are retarded on addition of anions like HSO;, SO;-, or CIO;, but they are accelerated on the addition of Mn(I1) ions. Interpretations of the above observations are furnished.

Vinyl polymerization of acrylonitrile by the Ce(IV)-glucose redox system

“…Termination of vinyl polymerization by metal ions (linear) is now well recognized [12,13]. A perusal of results reported in our earlier publications [8,9] indicates that both types of termination, i. e., mutual and linear are operative. At lowerconcentration of Ce(IV), mutual termination predominates over the linear one and at higher concentration, however, linear termination predominates over the mutual one.…”

“…In a series of interesting communications many workers [7] have shown that most organic compounds react with Ce(IV) to form free radicals which are capable of initiating vinyl polymerization. From this laboratory, we have reported the aqueous polymerization of acrylonitrile [8] and acrylamide [9] by the use,of Ce(IV) paired with glycerol. Although various other reducing agents have been used, no attempt has so far been made to use sugars as reducing agents.…”

Tl(III) initiated polymerization of methyl methacrylate in micellar phase

“…Such types of square-root dependence of R P(obs) on other metal ions were also reported earlier. [15][16][17] The resulting rate enhancement may be attributed to the preference of Tl(III) to be present at the micellar surface because of the electrostatic attraction of Tl(III) for the Stern region. The rate of Tl(III) consumption indicated linear dependence on Tl(III) concentration and is in good agreement with the findings of Santappa et al 4 for Tl(III)-initiated acrylamide polymerization.…”

“…This value is in good agreement with earlier reports for other redox systems. [15][16][17] At higher concentration of monomer, its interaction with SDS micelles is increased, which leads to the probability of their presence at reaction site (i.e., micellar core) in larger numbers, resulting in rate enhancement. The rate of Tl(III) disappearance, ϪR Tl , remained constant with the change in the monomer concentration (Table II), showing that Tl(III) was not directly involved in the initiation process.…”