K. Venkatarao

Peroxo salts as initiators of vinyl polymerization—2. Kinetics of polymerization of acrylic acid and sodium-acrylate by peroxodisulphate in aqueous solution—effect of pH and Ag+ catalysis

Results on the rate of polymerization of acrylic acid by S2O2−8 ion in alkaline and acid conditions are presented. Rp depended upon [S2O2−8]12 and [monomer]32 both in acid and alkaline solutions. The influence of ionic strength, the effect of pH on Rp and the catalytic effect of Ag+ and Cu2+ on the system have been discussed. Suitable mechanisms are proposed.

Decomposition of peroxodisulphate in aqueous alkaline solution

Abstract Results on the decomposition of S2O82− ion in highly alkaline conditions are presented. The rate of S2O82− disappearance RS2O82−, is found to be proportional to [OH−] and it is also possible to differentiate between two pathways of decomposition (i) homolytic cleavage of S2O82− to give SO4.− radicals and (ii) alkaline hydrolysis of S2O82− to give HSO4− and SO52−. The effect of ionic strength of the medium on these strength of the mediumm on these two reactions is discussed. Thermodynamic activation parameters, ΔH≠ and ΔS≠ have been calculated for these two reactions. The proposed mechanism is discussed in terms of the kinetic results.

Polymerization of N,N′-methylenebisacrylamide initiated by CEIV-thiourea redox system

Abstract The kinetics of polymerization of the symmetrical non-conjugated divinyl monomer N,N′-methylenebisacrylamide has been studied using CeIV-thiourea redox system as initiator. The rate of polymerization, Rp is proportional to [ Ce IV ] 1 2 , [ thiourea ] 1 2 and [ monomer ] 3 2 . A cyclopolymerization mechanism fits in with the experimental results.

Kinetics of Cyclopolymerization of N,N′-Methylenebisacrylamide Initiated by Redox Couples with Mn(III). Part II. Mn(III) with Ethylene Glycol or Mercaptoethanol

Abstract Cyclopolymerization kinetics of the nonconjugated divinyl monomer N,N′-methylenebisacrylamide (MBA) initiated by two different redox systems, trisacetatomanganese(III) dihydrate with either ethylene glycol or mercaptoethanol, in aqueous acetic acid at 35–50°C were investigated. Rates of polymerization and manganic ion disappearance were measured, and rate equations were derived from the observed dependence. Rate parameters were correlated with the differences in the reactivities of the radicals produced by the two systems toward the monomer and the metal ion. The rate of polymerization of MBA was compared with that of analogous monovinyl monomers.

Kinetics of Cyclopolymerization of N,N′-Methylenebisacrylamide Initiated by Redox Couples with Mn(III). Part I. Mn(III) with Glycerol

Abstract The polymerization kinetics of the divinyl monomer N,N′-methylenebisacrylamide (MBA) in aqueous acetic acid with the manganic acetateglycerol (GLY) redox system was investigated. The rate of polymerization, Rp , was proportional to [monomer]3/2 [Mn(III)]0.5 and [GLY]0.5. The rate of manganic ion disappearance, Rm , was directly proportional to [Mn(III)] and [GLY] but independent of monomer. Based on these results, a reaction mechanism which involves complex formation between Mn(OH)2+ and GLY, cyclopolymerization of the growing radicals, and mutual termination was proposed. The rate of polymerization was compared with those for analogous monovinyl monomers.

Peroxo salts as initiators of vinyl polymerization: Polymerization of acrolein initiated by potassium peroxodiphosphate

Abstract Kinetic studies were made on the polymerization of acrolein initated by potassium peroxodiphosphate (PP) in aqueous solution, in the presence and absence of Ag+ ions. The rate of polymerization was found to depend on [ M ] 3 2 (M = monomer) and was independent of both [PP] and [Ag+]. The overall activation energy was calculated to be 4.8 kcal mol−1. A mechanism involving termination by PO2-4 radicals is proposed and discussed.

Peroxo Salts as Initiators of Vinyl Polymerization. 6. Kinetics of Polymerization of Acrylonitrile Initiated by Potassium Peroxodisulfate in Aqueous Medium-Ag+ Catalysis

Abstract The kinetics of polymerization of acrylonitrile initiated by potassium peroxodisulfate in neutral and acid conditions was studied. Rp depended upon [S2O8 2-]1/2 and [monomer]3/2 both in neutral and acid solutions. The influence of ionic strength and the cata-lytic effect of Ag+ on the System are discussed. Suitable mech-anisms are proposed.

Kinetics of Cyclopolymerization of N,N′-Methylenebisacrylamide Initiated by Redox Couples with Mn(III). Part III

Abstract Redox-initiated free-radical cyclopolymerization of the nonconjugated divinyl monomer N,N′-methylenebisacrylamide was studied at 25–40°C, involving trisacetatomanganese(III) dihydrate as oxidant with four different reductants, methyl ethyl ketone (2-butanone), cyanoacetic acid, malic acid, and thiomalic acid. While the general mechanistic sequence is the same, the modes of termination are different in these cases. Because the reactivities of the different free radicals from the four redox pairs are different, the kinetic order with respect to the monomer, oxidant, and reductant differ considerably in magnitude. The kinetic and thermodynamic parameters were calculated.

Kinetics of Polymerization of Methyl Methacrylate Initiated by the Potassium Peroxodisulfate-Malonic Acid Redox System Catalyzed by Ag(l)

Abstract The kinetics of polymerization of methyl methacrylate (MMA) initiated by the potassium peroxodisulfate (K2S2O8)-malonic acid (MA) redox system catalyzed by Ag(I) was studied in aqueous solution at 35°C. The rate of polymerization (R) was proportional to [MMA]1.4, [K2S2O8]0.27, [MA]0.23, and [Ag+]0.5. The overall energy of activation was calculated to be 13.5 kcal·K−1·mol−1 between 20 and 45°C.