Aqueous polymerization of acrylonitrile initiated by the bromate–thiourea redox system

The aqueous polymerization of acrylonitrile initiated by an acidified bromate–thiourea redox system has been studied under nitrogen atmosphere. The rate of polymerization is independent of thiourea concentration over the range 2–9 × 10^?3M and reaches maximum at 9 × 10^?3M. The rate varies linearly with [monomer]. The initial rate of polymerization as well as the maximum conversion increases within the range of 4–22.5 × 10^?3M KBrO₃, but beyond 22.5 × 10^?3M the rate of polymerization decreases. The initial rate and the limiting conversion increases with increasing polymerization temperature in the range 30–45°C; and beyond 45°C they decrease. The effect of certain neutral salts, water-soluble solvents, and micelles of cationic, anionic, and nonionic surfactants on the rate of polymerization has been investigated.     

Aqueous polymerization of methacrylamide

The aqueous polymerization of methacrylamide (I) initiated by KBrO₃–thioglycolic acid (TGA) has been studied at 30 ± 0.2°C in nitrogen. The rate is given by K[M]^1.19 [thioglycolic acid]¹ [KBrO₃]^0.53 for 10–15% conversion. Activation energy was found to be 53.96 kJ/mole (12.92 kcal/mole) in the investigated range of temperature 30–45°C. The role of addition of a series of aliphatic alcohols and some salts was also determined. The kinetics of polymerization was followed iodometrically.     

Aqueous polymerization of acrylamide initiated by acidic potassium permanganate–ascorbic acid redox system

The polymerization of acrylamide initiated by the acidic permanganate–ascorbic acid redox pair has been studied in aqueous media at 30 ± 0.2°C in nitrogen atmosphere. The initial rate of polymerization has been found to be proportional to nearly the first power of the catalyst KMnO₄ concentration within the range 6.0 × 10^?3–14.0 × 10^?3 mole/l. The rate is proportional to the first power of the monomer concentration within the range 4.00 × 10^?2–12.0 × 10^?2 mole/l. However, the rate of polymerization is independent of ascorbic acid concentration within the range 3.0 × 10^?3–6.0 × 10^?3 mole/l., but the further increase of the concentration depresses the rate of polymerization as well as maximum conversion. The initial rate increases but the maximum conversion decreases as the temperature is increased within the range 20–35°C. The overall energy of activation has been found to be 9.8 kcal/mole. The optimum amount of sulfuric acid is essential to initiate the polymerization but its presence in excess produces no effect either on the rate of reaction or the maximum conversion. Water-miscible organic solvents and salts, e.g., CH₃OH, C₂H₅OH, (CH₃)₂CHOH, KCl, and Na₂SO₄, depress the rate. Slight amounts of MnSO₄ · H₂O and a complexing agent NaF increase the rate of polymerization. Cationic and anionic detergents have been found to decrease and increase the rate, respectively, while nonionic surfactants have no effect on the rate of polymerization.     

Aqueous polymerization of methacrylamide with potassium persulphate/thiomalic acid redox pair

Summary Methacrylamide was polymerized in aqueous medium at 35 ± 0.2 °C with the redox pair K₂S₂O₈/ thiomalic acid (mercaptosuccinic acid) in dark under nitrogen atmosphere. The effect of monomer, K₂S₂O₈ and thiomalic acid concentrations and temperature on the rate of polymerization was studied. The kinetics of polymerization was followed iodometrically.The role of the addition of complexing metal ions and a series of aliphatic alcohols was also investigated. The initial rate of polymerization was found to be independent of the concentration of thiomalic acid. Rate may be expressed by the following equation:R _p [M]^1.5[K₂S₂O₈]^0.76. The energy of activation was found to be 9.0 Kcal/deg/mole.With 4 figures     

Aqueous polymerization of methyl methacrylate initiated by peroxydisulfate–citric acid redox system catalyzed by silver ion

The kinetics of the aqueous polymerization of methyl methacrylate initiated by potassium peroxydisulfate–citric acid catalyzed by silver ion was investigated in nitrogen atmosphere. The rate of polymerization is proportional to the square root of peroxydisulfate concentration. The initial rate increases with increasing citric acid concentration up to 15 × 10^?3M, after which it decreases. The rate of polymerization also increases initially with monomer concentration and decreases at higher monomer concentration. The effects of temperature and the addition of some solvents and salts on the rate of polymerization have also been studied and a suitable kinetic scheme has been proposed for the reaction.     

Aqueous polymerization of acrylonitrile initiated by manganese(III) pyrophosphate-thiocyanate redox system: a kinetic study

Summary The kinetics of aqueous polymerization of acrylonitrile monomer (M) initiated by the Mn^III-KNCS redox system have been studied under deaerated conditions in the temperature range 26–40 °C at constant ionic strength. The overall rates of polymerization and the disappearance of Mn^III were determined. The polymerization was initiated by the free radicals arising from the Mn^III-thiocyanate redox reaction. The rate of polymerization was investigated at various concentrations of monomer and initiator. The effects of varying [Mn^III], [NCS^–], pH, total [P₂O _inf7 ^sup4– ], added [Mn^II], metal ions, ClO _inf4 ^sup– , Cl^– and SO _inf4 ^sup2– were examined. Dependence of the rate of polymerization on temperature was studied and activation parameters were computed from an Arrhenius plot. A suitable kinetic scheme consistent with the observed results is proposed and discussed.     

Aqueous polymerization of methacrylic acid initiated by Ce4+ -glycolic acid redox pair

The aqueous polymerization of methacrylic acid (MAA) initiated by a Ce⁴⁺ -glycolic acid (GA) system was observed in a sulfuric acid medium at 35 ± 0.2°C in a nitrogen atmosphere. The rate of monomer disappearance was proportional to [MAA]¹ and the rate of ceric ion disappearance was proportional to [GA][Ce⁴⁺]. An increase in the reaction temperature from 30 to 45°C raised the rate and the overall activation energy was 63 kJ/mol. The molecular weight increased with a rise in [MAA] and a reduction in [Ce⁴⁺]. The effect of varying [H₂SO₄] was also studied.     

Aqueous polymerization of acrylamide initiated by cerium (IV)–ethylenediamine tetraacetic acid redox system

Ethylenediamine tetraacetic acid (EDTA) terminated polyacrylamide was obtained by using the EDTA–cerium(IV) ammonium nitrate [Ce(IV)] redox initiator in the aqueous polymerization of acrylamide. The polymerization behaviors as a function of the concentration of Ce(IV), EDTA, and acrylamide as well as temperature were studied. The consumption rate of cerium(IV) depends a first-order reaction on the ceric ion concentration ([Ce(IV)]). The complex formation constant (K) and disproportionation constant (k_d) of Ce(IV)–EDTA chelated complex are 1.67 × 10⁴ and 3.77 × 10^?3, respectively. The rate dependences of polymerization on monomer concentration and EDTA concentration both follow a second-order reaction in the run of initial monomer concentration ([M]_i) equal to 0.2 mol dm^?3. The number average molecular weight increases linearly with the ratio of [M]_i/[Ce(IV)]_i. The mechanism and kinetics for the polymerization was proposed. The kinetic parameters involved were determined. © 1992 John Wiley & Sons, Inc.     

Aqueous polymerization of acrylonitrile initiated by the Mn3+/citric acid redox system

Kinetics of polymerization of acrylonitrile initiated by the redox system Mn³⁺/citric acid were investigated in aqueous sulphuric acid in the range of 20–25°; initial rates of polymerization and Mn³⁺ disappearance etc. were measured. The effects of certain water miscible organic solvents and certain cationic and anionic detergents on the rate of polymerization have been examined. A mechanism has been suggested involving formation of a complex between Mn³⁺ and citric acid, decomposition of which yields the initiating free radical and with polymerization being terminated by mutual interaction of growing radicals.     

Kinetics of polymerization of acrylonitrile initiated by acidic permanganate/thioacetamide redox system

The kinetics of vinyl polymerization of acrylonitrile (AN) initiated by an acidic permanganate/thioacetamide (TAm) redox system have been investigated in aqueous media at 30 ± 0.2°C in nitrogen, and the rate of polymerization measured. The effect of additives like organic solvents, neutral electrolytes, and complexing agents on the rate have been assessed. Based on the experimental results, a suitable reaction scheme involving initiation by organic free radicals generated by the interaction of Mn(IV) with protonated thioacetamide and termination by Mn(III) has been suggested. Various rate and energy parameters have been evaluated.     

Aqueous polymerization of acrylonitrile by ascorbic acid–peroxodisulfate redox system

The polymerization of acrylonitrile initiated by an ascorbic acid–peroxodisulfate redox system was studied in an aqueous solution at 35°C in the presence of air. Molecular oxygen was found to have no effect on the polymerization reaction. An increase in ionic strength slightly increased the rate. The overall rate of polymerization, R_p, showed a square dependence on [monomer] and a half-order dependence on [peroxodisulfate]. A first-order dependence on [ascorbic acid] at low concentrations (<3.0 × 10^?3 mol L^?1) followed by a decrease in R_p at higher concentrations of ascorbic acid (>3.0 × 10^?3 mol L^?1) was also noted. R_p remained unchanged up to 40°C and showed a decline thereafter. Addition of catalytic amounts of cupric ions decreased the rate whereas ferric ions were found to increase the rate. Added sulfuric acid in the range (6.0?50.0) × 10^?5 mol L^?1 decreased the R_p.     

Kinetics of polymerization of acrylonitrile initiated by the Mn3+-thioacetamide redox system

Kinetics of the polymerization of acrylonitrile has been investigated in aqueous sulfuric acid in a temperature range of 25–45°C. The rate of polymerization (R_p) and the rate of managanic ion disappearance, etc., have been measured. The effect of the various additives, such as water-miscible organic solvents, neutral electrolytes, complexing agents, and surfactants, on the rate has been thoroughly studied. A mechanism that involves the initial complex formation between the thiol form of the thioamide and Mn³⁺, whose decomposition yields the initiating free radical with the polymer chain terminated by mutual combination of growing radicals, has been suggested.     

Emulsion polymerization of vinyl acetate initiated by potassium persulfate-cyclohexanone sodium bisulfite redox pair system

The emulsion polymerization of vinyl acetate using potassium persulfate and cyclohexanone sodium bisulfite as redox pair initiation system was studied. The rate of polymerization, maximum conversion, and the number of polymer particles produced were found to change with redox initiator, monomer and emulsifier concentrations, and temperature variation. The rate of polymerization was found to be dependent on the initiator, the monomer, and the emulsifier concentrations to the 0.88, 0.22, and 0.20 powers, respectively. The K₂S₂O₈–NaHSO₃ redox system was found to decrease maximum conversion and doesn't form a stable emulsion. The apparent arrhenius activation energy (E^a) estimated for the polymerization system was 65.6 kJ/mol. The viscosity average molecular weights for some obtained poly(vinyl acetate) were determined.     

Vinyl polymerization initiated by peroxydiphosphate. VII. Polymerization of acrylonitrile initiated by peroxydiphosphate–ascorbic acid redox system

The polymerization of acrylonitrile was studied with a peroxydiphosphate–ascorbic acid redox system as the initiator. The rate of polymerization increased with increasing peroxydiphosphate concentration and the initiator exponent was computed to be 0.5. It also increased with increasing monomer concentration and the monomer exponent was computed to be unity. The reaction was carried out at three different temperatures and the overall activation energy was computed to be 4.6 kcal/mol. The effect of certain surfactants on the rate of polymerization was investigated and a suitable kinetic scheme is described.     

Role of N,N-dimethyl-para-toluidine and saccharin in the radical polymerization of methyl methacrylate initiated by a redox system. I. Cumene hydroperoxide/copper saccharinate

Kinetics of methyl methacrylate polymerization initiated by a redox system [cumene hydroperoxide (CHP)/copper saccharinate] were studied in bulk at 20°C in the presence of accelerators such as N,N-dimethyl-p-toluidine (DMPT) and o-benzoic sulphimide (saccharin). Assuming a steady-state concentration of propagating radicals, the polymerization rate depends on the square root of the initiation rate and the kinetic orders with respect to each compound in the initiation step may be deduced. Initiation is first-order in CHP, copper saccharinate, and saccharin and second-order in DMPT. A reaction scheme consistent with these orders is proposed. The main features are the following: (1) CHP reduces rapidly Cu(II) to Cu(I); (2) a small fraction of Cu(I) is complexed with DMPT; (3) the complexed ions (Cu⁺, DMPT₂) are strong reductants with respect to CHP whereas uncomplexed Cu⁺ are almost inactive; (4) the decomposition of CHP is strongly catalyzed by saccharin (protonated CHP is 13000 times more reactive than free CHP). Thus both accelerators are necessary to get high polymerization rates. © 1994 John Wiley & Sons, Inc.     

Role of N,N-dimethyl-para-toluidine and saccharin in the radical polymerization of methyl methacrylate initiated by a redox system. II. Cumene hydroperoxide/iron saccharinate

The role of N,N-dimethyl-p-toluidine (DMPT) and saccharin as accelerators in the polymerization of methyl methacrylate initiated by the redox decomposition of cumene hydroperoxide (CHP) in the presence of iron saccharinate has been kinetically investigated. DMPT reduces ferric ions to ferrous ions, so that an equilibrium is established between the two oxidation states. With the assumption of a steady-state concentration of propagating radicals, the rate of initiation was deduced from the rate of polymerization and the kinetic orders with respect to each compound involved in the initiation step have been determined. The reaction is first-order in CHP, iron saccharinate, and saccharine and second-order in DMPT. In a proposed scheme, Fe²⁺ ions, complexed by two DMPT molecules, are much more reactive than uncomplexed Fe²⁺ and saccharin activates the decomposition of CHP by protonation of the O? O bond. This mechanism, similar to that proposed in the case of copper saccharinate, explains the synergistic effect of both accelerators. © 1994 John Wiley & Sons, Inc.     

Aqueous polymerization of acrylamide initiated by cerium(IV)–amino acid chelating agent redox initiators

Amino acid-type chelating agents such as nitrilotriacetic acid (NTA), nitrilotripropionic acid (NPA), iminodiacetic acid (IDA), and ethylenediamine tetraacetic acid (EDTA) were used in combination with cerium(IV) ammonium nitrate [Ce(IV)] as the redox initiators for the aqueous polymerizations of acrylamide (AM). The polymerization behaviors and polymer qualities were studied as functions of the concentrations of Ce(IV), chelating agent, AM, as well as temperature. The performances of the chelating agent redox systems varied with the natures of the chelating agents. The NTA–Ce(IV) initiator showed the most promising polymerization rate and conversion. The blank tests for the reactions of cerium and chelating agents were also conducted for finding mechanism of formation of free radicals and determining their complex formation constants (K) and disproportionation constants (k_d). The mechanism for the polymerization was proposed and the kinetic parameters were evaluated. © 1993 John Wiley & Sons, Inc.     

Aqueous polymerization of ethyl acrylate initiated by ceric ion-reducing agent system in sulphuric acid medium

Kinetic study of aqueous polymerization of ethyl acrylate (EA) is carried out at 30 °C in dilute sulphuric acid medium by employing ammonium ceric sulphate–methyl ethyl ketone (MEK) as redox initiator system. The ceric ion consumption is found to be first order with respect to ceric ion and half order with respect to reducing agent concentrations. No complex formation between ceric ion and reducing agent is observed. The orders with respect to ceric ion, reducing agent and monomer concentrations are evaluated for the aqueous polymerization of EA by Ce(IV)–MEK redox initiator system, and are found to be 0.5, 0.5 and 1.4, respectively . The overall activation energy, E _overall, for aqueous polymerization of EA in the temperature region of 27–40°C is found to be 20.27 kJ/mol. A kinetic scheme for the aqueous polymerization of EA initiated by Ce(IV)–MEK redox initiator system is presented.This revised version was published online in June 2005 with corrections to figure legends as well as small corrections within text.