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.     

Studies of redox polymerization. I. Aqueous polymerization of acrylamide by an ascorbic acid–peroxydisulfate system

The polymerization of acrylamide initiated by an ascorbic acid–peroxydisulfate redox system was studied in aqueous solution at 35 ± 0.2°C in the presence of air. The concentrations studied were [monomer] = (2.0–15.0) × 10^?2 mole/liter; [peroxydisulfate] = (1.5–10.0) × 10^?3 mole/liter; and [ascorbic acid] = (2.84–28.4) × 10^?4 mole/liter; temperatures were between 25–50°C. Within these ranges the initial rate showed a half-order dependence on peroxydisulfate, a first-order dependence on an initial monomer concentration, and a first-order dependence on a low concentration of ascorbic acid [(2.84–8.54) × 10^?4 mole/liter]. At higher concentrations of ascorbic acid the rate remained constant in the concentration range (8.54–22.72) × 10^?4 mole/liter, then varied as an inverse halfpower at still higher concentrations of ascorbic acid [(22.72–28.4) × 10^?4 mole/liter]. The initial rate increased with an increase in polymerization temperature. The overall energy of activation was 12.203 kcal/mole in a temperature range of 25–50°C. Water-miscible organic solvents depressed the initial rate and the limiting conversion. The viscometric average molecular weight increased with an increase in temperature and initial monomer concentration but decreased with increasing concentration of peroxydisulfate and an additive, dimethyl formamide (DMF).     

Polymerization of Acrylamide with Permanganate/Mercaptosuccinic Acid Initiator System

The aqueous polymerization of acrylamide initiated by the acidified potassium permanganate/mercaptosuccinic acid redox system was studied at 35 ± 0.2°C in nitrogen. In the studied range of activator concentration (2.0 × 10^?3 to 6.25 ± 10^?3 mole/liter) the polymerization rate remains unaffected. The initial rate of polymerization varies linearly with KMnO₄ and acrylamide concentrations in the studied range. The activation energy was found to be 6.61 kcal/mole (27.63 kJ/mole) in the temperature range of 30–50°C. The molecular weight of polyacrylamide was found to be independent of [KMnO₄] but increased with increasing monomer concentration. The effect of DMF on polymerization rate and molecular weight was also investigated.     

The Effect of Active Carbon on the Kinetics of Polymerization of Methyl Methacrylate

Rates of 2–2¹?azobisisobutyronitrile initiated polymerization of methyl methacrylate in benzene were determined at 77.2, 65.0, and 50.0°C. The variation of molecular weight of the polymer with temperature and conversion was also studied. At a fixed conversion of 2.0%, the molecular weight decreased from 2.05 × 10⁵ at 50°C to 1.4 × 10⁵ at 77.2°C. The ratio of the propagation rate coefficient to the square root of the termination rate coefficient was found to be 0.61, 0.397, and 0.374 at 77.2, 65.0, and 50.0°C, respectively, with an uncertainty of ±0.5°C in temperature. The effect of active carbon on the rates of polymerization at 77.2°C was measured. Rates of polymerization decreased in the presence of active carbon. For example, the initial rate of polymerization decreased from 7.8 × 10^?4 mole/(liter min) to 4.6 × 10^?4 mole/(liter min) when the carbon concentration was varied from 0 to 9.65 g/liter. The molecular weight of the polymer increased from an average of 1.4 × 10⁵ in the absence of carbon to 1.5 × 10⁵ when carbon was present.     

Aqueous Polymerization of Methyl Methacrylate Initiated by Potassium Peroxydisulfate-Ascorbic Acid Redox System

The aqueous polymerization of methyl methacrylate initiated by the redox system K₂S₂O₈-ascorbic acid has been studied at 35°C under the influence of oxygen. The rate of polymerization increases with increasing ascorbic acid concentration at low activator concentration, remains constant within the range 4.375 × 10^?3 to 11.25 × 10^?3 mole/liter, and at higher ascorbic acid concentration again decreases. The rate varies linearly with monomer concentration. The initial rate and the limiting conversion increase with increasing polymerization temperature. Organic solvents (water-miscible only) and small amounts of neutral salts like KC1 and Na₂SO₄ depress the initial rate and the maximum conversion. The addition of small amounts of salts like Cu²⁺ and Mn²⁺ increases the initial rate, but no appreciable increase in the limiting conversion is observed.     

Polymerization of acrylamide with persulfate–thiomalic acid initiator

The redox system of potassium persulfate–thiomalic acid (I₁–I₂) was used to initiate the polymerization of acrylamide (M) in aqueous medium. For 20–30% conversion the rate equation is where R_p is the rate of polymerization. Activation energy is 8.34 kcal deg^?1 mole^?1 in the investigated range of temperature 25–45°C. M_n is directly proportional to [M] and inversely to [I₁]. The range of concentrations for which these observations hold at 35°C and pH 4.2 are [I₁] = (1.0–3.0) × 10^?3, [I₂] = (3.0–7.5) × 10^?3, and [M] = 5.0 × 10^?2–3.0 × 10^?1 mole/liter.     

Effect of pyridine on the kinetics of polymerization of methyl methacrylate initiated by benzoyl peroxide and azobisisobutyronitrile at 60°C

Solution polymerization of MMA, with pyridine as the solvent and BZ₂O₂ and AIBN as thermal initiators, was studied kinetically at 60°C. The monomer exponent varied from 0.45 to 0.91 as [BZ₂O₂] was increased from 1 × 10^?2 to 30 × 10^?2 mole/liter in a concentration range of 8.3-4.6 mole/liter for MMA. For AIBN-initiated polymerization the monomer exponent remained constant at 0.69 as [AIBN] varied from 0.4 × 10^?2 to 1.0 × 10^?2 mole/liter in the same concentration range for MMA. The k²_p/k_t Value increased in both cases with an increase in pyridine concentration in the system. This was explained in terms of an increase in the k_p value, which was due presumably to the increased reactivity of the chain radicals by donor-acceptor interaction between the molecules of solvent pyridine and propagating PMMA radicals and in terms of lowering the k_t value for the diffusion-controlled termination reaction due to an increase in the medium viscosity and pyridine content.     

Polymerization of acrylonitrile: Kinetics of the reaction initiated by the Fe2+/BrO3− redox system

The aqueous polymerization of acrylonitrile initiated by the bromate—ferrous redox system in aqueous sulfuric acid was studied under nitrogen atmosphere. The rate of polymerization increased with increasing concentration of ferrous in the range of 0.25-1 × 10^?2M. The percentage of conversion increased with increasing concentration of the catalyst, but beyond 2.5 × 10^?3M there was a decreasing trend in the rate of polymerization. The rate varied linearly with [monomer]. The initial rate of polymerization as well as the maximum conversion increased within the range of 1–2.5 × 10^?3M KBrO₃, but beyond 2.5 × 10^?3M the rate of polymerization decreased. The initial rate and limiting conversion increased with increasing polymerization temperature in the range 30–40°C; beyond 40°C they decreased. The effect of certain neutral salts, water-miscible solvents, complexing agents, and copper sulfate concentration on the rate of polymerization was investigated.     

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.     

Ferric oxide-catalyzed polymerization of methyl methacrylate

The polymerization of methyl methacrylate was carried out in water at various concentrations of sodium bisulfite, ferric oxide, and methyl methacrylate at 30, 40, and 50°C. The effect of ferric oxide on the rate of polymerization was studied at 50°C. Rates of polymerization increased in the presence of ferric oxide. For example, the rate of polymerization increased from 3.4 × 10^?5 mole/l.-sec to 11.8 × 10^?5 mole/l.-sec when the ferric oxide concentration was varied from 0 to 15 g/l. water. The molecular weight of the polymer decreased from an average of 1.4 × 10⁶ in the absence of ferric oxide to 2.8 × 10⁵ when the ferric oxide was present. The variation of molecular weight of the polymers with temperature and conversion was studied. At a fixed conversion of 80%, the average molecular weight decreased from 3.4 × 10⁵ at 30°C to 2.2 × 10⁵ at 50°C. The average molecular weight was also found to increase with increasing monomer and initiator concentrations. It increased from 8.1 × 10⁴ to 5.3 × 10⁵ and from 3.4 × 10⁵ to 8.9 × 10⁵ as the initiator and monomer concentrations increased from 0.01 to 0.05 mole/l. and from 0.235 to 0.705 mole/l., respectively. The apparent energy of activation for the polymerization was found to be 15.6 and 9.7 kcal/mole in absence and in presence of ferric oxide, respectively.     

Molecular weight distributions in radiation-induced polymerization. III. γ-Ray-induced polymerization of styrene at low temperatures

The kinetics of the γ-radiation-induced polymerization of styrene was studied at radiation intensities of 8 × 10⁴, 2.4 × 10⁵, 3.1 × 10⁵, and 8.3 × 10⁵ rad/hr over a temperature range of ?10°C to 30°C. The water content of the irradiated samples varied from 1.0 × 10^?3 to 7.5 × 10^?3 mole/l. The power dependence of the rate of polymerization on the dose rate at ?10°C varied from 0.53 to 0.71 as the water content of the sample varied from 7.5 × 10^?3 to 1.0 × 10^?3 mole/l. A value of 3.1 kcal/mole was determined for the overall activation energy. Molecular weight distribution studies by gel-permeation chromatography indicated the presence of two distinct peaks. The contribution of each peak was dependent on specific experimental parameters. Kinetic data and molecular weight distribution data indicate the coexistence of two propagating species. Analysis of the data strongly suggests that a free-radical mechanism and a cationic mechanism are involved.     

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.     

Polymerization of Acrylonitrile Initiated by 1,4-Dimethyl-1,4-bis(p-nitrophenyl)-2-tetrazene

The polymerization of acrylonitrile (AN) initiated by 1,4-dimethyl-1,4-bis(p-nitrophenyl)-2-tetrazene (Ie) was studied in dimethylformamide (DMF) at high temperature. The polymerization proceeds by a radical mechanism. The rate of polymerization is proportional to [Ie]^0.64 and [AN]^1.36. The overall activation energy for the polymerization is 21.5 kcal/mole within the temperature range of 115-130°C. The chain transfer of Ie was also undertaken over the temperature range of 120-135°C. The activation parameters for the decomposition of Ie at 120°C are k_d = 2.78 × 10^?6 sec^?1, ΔH^? = 40.8 kcal/mole, and ΔS^? = 19.5 cal/mole-deg, respectively.     

Persulfate-initiated polymerization of acrylamide

A dilatometric technique was used to obtain conversion–time data for the polymerization of acrylamide initiated by potassium persulfate in water. The results are summarized by the empirical rate expression, ?d[M₁]/dt = R_p = k_1.25[K₂S₂O₈]^0.5[M₁]^1.25, and k_1.25 = 1.70 × 10¹¹ exp {?16,900/RT} 1.^0.75/mole^?0.75-min. Persulfate was varied over the range 9.5 × 10^?4 to 5.2 × 10^×2 mole/l., and initial monomer concentration [M₁] was varied from 0.05 to 0.4 mole/l. The temperature range was 30?50°C. Results of analysis of the kinetics and energetics of the polymerization favor a cage-effect theory rather than a complex-formation theory to explain the order with respect to monomer.     

Aqueous Polymerization of Methyl Methacrylate Initiated by the Bromate-Thiourea Redox System

The aqueous polymerization of methyl methacrylate initiated by the bromate-thiourea redox system in dilute HC1 has been investigated under nitrogen atmosphere. The rate of polymerization increases with increasing concentration of thiourea in the range 5 × 10^?3?10 × 10^?3 M. The percentage of conversion increases with increasing concentration of the catalyst, but beyond 1.5 × 10^?2 M, there is a decreasing trend in the rate of polymerization. The rate of polymerization increases with increasing monomer concentration, but beyond 0.184 M the polymerization rate decreases due to gel effect. The rate of polymerization increases with temperature up to 35°C and beyond 40°C a decreasing trend is noticed. The effect of water miscible organic solvents, certain neutral salts on the rate of polymerization has also been investigated.     

Grafting vinyl monomers onto silk fibers. IX. Graft copolymerization of methyl methacrylate onto silk using peroxydiphosphate-thiourea redox system

The graft copolymerization of methyl methacrylate (MMA) onto silk in aqueous media initiated by the potassium peroxydiphosphate-thiourea redox system was studied at 50°C. The rate of grafting was determined by changing [monomerl], [thiourea], [initiator], acidity of the medium, reaction medium, and temperature. A significant increase percent of grafting was noticed with increasing monomer concentration to 84.49 × 10^?2 mole/liter and the further increase is associated with the decrease of graft yield. The graft yield increases with an increase of thiourea (Tu) concentration to 25 × 10^?5 mole/liter; then it decreases. A measurable increase in graft yield was observed with an increase in acidity of the medium. Graft yield increases to a certain temperature, i.e., 50°C, and then it decreases. The graft yield increases with an increase of initiator concentration to 60 × 10^?4 mole/liter; then it decreases. The graft yield is medium dependent. A suitable kinetic path has been proposed and the rate equation has been derived.     

Polymerization of vinyl acetate retarded by 4-methyl-2,6-di-tert-butylphenol: Kinetic and ESR studies

4-Methyl-2,6-di-tert-butylphenol strongly retards the free radical polymerization of vinyl acetate initiated by azobisisobutyronitrile. The chain transfer constant, estimated from rate data, is 0.020 ± 0.004 at 35°C and does not vary significantly with temperature. Molecular weight data lead to transfer constants of 0.023, 0.020, and 0.024 at 35, 45, and 55°C, respectively. A mean kinetic isotope effect of 9.8 ± 1.0 is observed for the phenol deuterated at the OH group, showing that the main attack of poly(vinyl acetate) radicals on the phenol involves hydrogen abstraction from this group. The activation energy for hydrogen abstraction is estimated to be 7.8 kcal/mole, and the rate constant at 50°C is 160 ± 40 1./mole-sec. The stationary concentration of 4-methyl-2,6-di-tert-butylphenoxyl in the polymerization mixture is proportional to the phenol concentration and is independent of the initiator concentration, as shown by electron spin resonance studies. Cross termination of poly(vinyl acetate) and phenoxy radicals occurs to a greater extent than mutual termination of these radicals. The rate constant for cross termination is close to 1 × 10⁸ 1./mole-sec at 50°C; the activation energy for cross termination is 2.9 ± 1.3 kcal/mole.     

Aqueous Polymerization of Methyl Methacrylate

Aqueous polymerization of methyl methacrylate (MMA), initiated by the potassium bromate-thioglycollic acid (TGA) redox system, has been studied at 30 ± 0.2° C under positive pressure of nitrogen. The rate is given by K[MMA] [TGA] ⁰[KBrO₃]^x where × = 1 for lower KBrO₃ concentrations and 0.5 for higher KBrO₃ concentrations. The reaction has been studied over the 20–45°C range. The activation energy was found to be 65.72 kJ/mol (15.71 kcal/mol) in the investigated range of temperature. Inorganic electrolytes except MnSO₄·4H₂O and Na₂C₂O₄ depress both the rate of polymerization and the maximum conversion. All the alcohols (viz., MeOH, EtOH, iso-PrOH, tert-BuOH) and acetone depress the rate of polymerization as well as the maximum conversion.     

Polymerization of Methacrylamide Initiated by the Persulfate/Thiolactic Acid Redox System

The aqueous polymerization of methacrylamide initiated by the ammonium persulfate/thiolactic acid redox system has been studied at 35 ± 0.2°C. The rate of polymerization is governed by the expression, R_p + K_p [MAA] ^1.33 [TLA]^0.22 [ammonium persulfate]^0.6. The deviations from normal kinetics are discussed. A tentative mechanism of initiation is given. The temperature dependence of the rate of polymerization has been studied over the range 30–55°C. The overall activation energy of polymerization is 10.4 kcal/mole.     

Effect of pyridine on the kinetics of polymerization of styrene initiated by benzoyl peroxide and azobisisobutyronitrile at 60°C

Kinetics of solution polymerization of styrene was studied using pyridine as solvent and BZ₂O₂ and azobisisobutyronitrile (AIBN) as initiators at 60°C. Normal kinetic features (R_p ∝ [AIBN]^0.5 · [styrene]^1.0) were observed for the AIBN-initiated polymerization, with pyridine playing the role of an inert diluent; but in the BZ₂O₂-initiated polymerization, the monomer exponent was found to vary from a low value of 0.45 at a relatively low initiator concentration (1 × 10^?2 mole/liter) to a value higher than the usual value of unity (1.18) at a much higher concentration of the initiator (16 × 10^?2 mole/liter). The initiator exponent value was found to be 0.5 (usual) up to 20% v/v dilution with pyridine, but it showed a tendency to decrease with increase in pyridine content beyond 20% v/v. The k/k_t value for each initiator system, however, was found to remain constant over the whole concentration range of pyridine. The unusual kinetic features were explained on the basis of predominance of one or the other of two competitive reactions in BZ₂O₂-initiated system: (a) higher rate of decomposition of BZ₂O₂ in pyridine and (b) primary radical depletion by reaction with pyridine, depending upon the concentration of BZ₂O₂ and pyridine.