Aqueous polymerization of methacrylamide initiated by KMnO4/H2C2O4 redox system

The polymerization of methacrylamide initiated by potassium permanganate/oxalic acid redox system has been studied at 35 ± 0.2°C in a nitrogen atmosphere. The rate of polymerization is independent of the activator (oxalic acid) concentration within the range 5·10^?3 to 10·10^?3 mole·1^?1, except at very high (above 10·10^?3 mole·1^?1) or at very low (below 5·10^?3 mole·1^?1) concentrations of the activator. The rate varies linearly at low monomer concentration (up to 5.87·10^?2 mole·1^?1). The catalyst exponent decreases from nearly unity (0.91) to 0.66 with increase in concentration of the catalyst (KMnO₄) probably due to participation of primary radicals in the termination of the growing chain. The addition of strong acid (H₂SO₄) within the range 5 · 10^?4–15 · 10^?4 mole · l^?1, shows a constant pH of 2.7 resulting in no change in initial rate. With activator alone (H₂C₂O₄ · 2H₂O), within the pH range 2.7 to 2.9 an optimum is observed. The initial rate increases with increase in polymerization temperature. The overall energy of activation as calculated from the ARRHENIUS plot has been found to be 15.1 kcal · mole^?1 within the temperature range 30–50°C. Organic solvents (water miscible only) depress the initial rate and the maximum conversion. Small amounts of neutral salts (KCl and Na₂SO₄), however, show no appreciable effect on the polymerization rate, but small amounts of manganous salts (MnSO₄) can increase the initial rate to a considerable extent. High concentrations of MnSO₄ result in termination of the growing chain. A complexing agent, Na₂F₂, decreases the initial rate but increases the maximum conversion. Introduction of fresh catalyst at intermediate stages of polymerization increases both the rate of the reaction and the conversion.     

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

The polymerization of methacrylic acid initiated by permanganate / oxalic 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 ((0.8-6.0)·10^?4 mole/l.) at low monomer concentration (5.89·10^?2 mole/l.) but the catalyst exponent varies from 1.2 to 0.2 at comparatively high monomer concentration (17.68·10^?2 mole/l.) and falls at comparatively higher concentrations of the activator ((COOH)₂) at constant concentration of catalyst (1.6·10^?4 mole/l.) and monomer (5.89·10^?2 mole/l.). The rate is proportional to the first power of the monomer concentration within the range (2.36–14.1)·10^?2 mole/l. and catalyst (2.8·10^?4 mole/l.). The initial rate increases with increase in polymerization temperature up to 45°C. The overall activation energy has been found to be 9.87 kcal/mole within the temperature range 30-45°C. Organic solvents (water miscible only) and salts (KCl, Na₂SO₄ and Na₂C₂O₄) depress the rate considerably but the manganous salt (MnSO₄) is found to increase the initial rate. A complexing agent, NaF, decreases the rate as well as the maximum conversion. Introduction of new catalyst at intermediate stages of polymerization increases the rate and the maximum conversion.     

Aqueous redox polymerization of acrylamide initiated by citric acid/permanganate

The homogeneous redox polymerization of acrylamide by the citric acid/permanganate initiating system was investigated at 35±0,2°C under nitrogen. Variation of the activator concentration in the range of 2,5.10^?3 to 20,0.10^?3 mol/dm³ had no effect on the rate of polymerization. The initial rate increased with the increasing catalyst concentration and a value of nearly unity of the catalyst exponent confirmed a unimolecular chain termination process. The rate varied linearly with the monomer concentration over a wide range (5,0.10^?2 to 20,0.10^?2mol/dm³). The initial rate increased with the increasing temperature but the maximum conversion showed a decrease as the temperature was raised above 35°C. The energy of activation, in the temperature range of 25 to 45°C, was found to be 55,90kJ/mol (13,36 kcal/mol). The addition of neutral salts, Co(NO₃)₂, Ni(NO₃)₂, organic solvents, and complexing agents, all water soluble, reduced the rate and percentage of conversion. The introduction of MnSO₄ or of more catalyst (at intermediate stages) into the system increased both the rate and limiting conversion.     

Aqueous polymerization of acrylic acid initiated by KMnO4 — H2C2O4 redox system

Polymerization of acrylic acid in aqueous solution initiated by permanganate-oxalic acid redox pair has been studied at 32 ± 0.2°C in nitrogen atmosphere. The rate of polymerization has been found to be nearly independent of oxalic acid concentration within the range 1.87 to 9.33 · 10^?3 mole/l. and decreases only at higher concentrations of the oxalic acid. The rate has also been found to vary with the first power of the monomer concentration (within the range 1.44 to 5.76 · 10^?2 mole/l.) and the first power of the catalyst concentration (8.0 to 28.0 · 10^?5 Mole/l.). It is, however, proportional to half power at relatively high catalyst concentration, at fixed concentrations of oxalic acid (1.03 · 10^?2 mole/l.) and the monomer (5.76 · 10^?2 mole/l.). At higher concentration of monomer the catalyst exponent has been found to be nearly unity for both the higher and lower concentrations of the catalyst. The initial rate of polymerization increases with increase in temperature. The overall energy of activation has been found to be 19.56 kcal/mole within the temperature range 30 – 45°C. Organic solvents and salts (KCI, Na₂SO₄, and Na₂C₂O₄) depress the rate but MnSO₄ 4H₂O has been found to increase the initial rate but depress the maximum conversion.     

Aqueous polymerization of acrylamide initiated by acidic permanganate/thiourea redox system

The polymerization of acrylamide, initiated by acidic permanganate/thiourea redox system, was studied in aqueous media at 30 ± 0,2 °C in nitrogen. The rate of polymerization (R_p) was found to be proportional to nearly the first power of the catalyst (KMnO₄) concentration, within the range of 0,5 · 10^?2 to 1,4 · 10^?2 mol dm^?3, and independent of the thiourea concentration. However, the rate of polymerization varies with the first power of the hydrochloric acid concentration within the range of 2,85 · 10^?2 to 11,4 · 10^?2 mol dm^?3, and increases linearly up to certain extent by varying the monomer concentration from 2,5 · 10^?2 to 12,5 · 10^?2 mol dm^?3. A deviation from the linear behaviour is observed, however, above a concentration of 12,5 · 10^?2 mol dm^?3. The initial rate of polymerization (R_i) as well as the maximum conversion increases by increasing the temperature up to 35 °C, but the maximum conversion falls as the temperature rises above 35 °C. The overall energy of activation is found to be 47,70 kJ mol^?1 (11,48 kcal/mol^?1) within the temperature range of 25–45 °C. Addition of salts, except manganous salts, was found to be associated with a depression in the R_p and maximum conversion. The effect of cationic and anionic surfactants has been found to increase and decrease the R_p respectively; non-ionic detergents, however, have no effect on the R_p.     

Aqueous polymerization of acrylamide initiated by acidic thiourea/potassium bromate redox system

The aqueous polymerization of acrylamide initiated by bromate/thiourea redox system has been studied in acidic media at 25 ± 0.2°C in a nitrogen atmosphere. The rate of polymerization has been found to vary with the first power of the potassium bromate concentration within the range 0.75·10^?2 to 2.0·10^?2 mole·1^?1 and nearly with the first power of the hydrochloric acid concentration within the range 2.85·10^?2 to 8.55·10^?2 mole·1^?1. However, the rate of polymerization is independent of the thiourea concentration, but varies with the first power of the monomer concentration within the range 6.0·10^?2 to 10.0·10^?2 mole·1^?1. The initial rate increases but the maximum conversion decreases as the temperature increases within the range 19 to 35°C. The over all energy of activation has been found to be 22.9 kcal·mole^?1 within the temperature range mentioned above. Water miscible organic solvents and mono- and dibasic salts show the same effect as given by MISRA et al. The effect of cationic and anionic surfactants has been found to increase and decrease the rate of polymerization (R_p) respectively, however non-ionic detergents have no effect on the (R_p).     

Kinetics of the aqueous polymerization of acrylamide initiated by the permanganate- tartaric acid redox system

The kinetics of the aqueous polymerization of acrylamide, initiated by the permanganate/tartaric acid redox system was studied at 35±0,2°C under nitrogen. The initial rate of polymerization remains independent of the tartaric acid concentration in the range 3,3.10^—3 to 9,9.10^—3mol/dm³. The order of the reaction with respect to the catalyst concentration (catalyst exponent) is found to be 0,55, indicating a bimolecular mechanism for the termination reaction. The rate of polymerization varies linearly at low monomer concentrations (1,25.10^—2 to 5,0.10^—2mol/dm³). With increase in temperature above 35°C, the initial rate increases but the conversion decreases. The overall energy of activation is found to be 18,68 kcal/mol (78,10kJ/mol) in the temperature range 30 to 50°C. Water miscible organic solvents and neutral salts depress both the rate and the conversion. Addition of MnSO₄ or the injection of more catalyst at intermediate stages raises both the initial rate and the maximum conversion. NaF decreases the rate but increases the conversion.     

Effect of some additions on the aqueous polymerization of acrylamide,initiated by permanganate-oxalic acid redox system

The effect of different additives on the aqueous polymerization of acrylamide, initiated by MnO-oxalic acid redox pair, was studied at 25°C in an atmosphere of nitrogen. It was observed that the rate of polymerization increased in the presence of alkali metal (Li⁺ to Rb⁺) chlorides. Cupric chloride and ferric chloride were found to be polymerization retarders. Anionic and cationic detergents showed marked influence on the rate of polymerization. Also, the presence of water-soluble alcohols lowered the polymerization rates to a sufficient extent.     

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

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 [M]^3/2, and R^1/2 at lower concentrations of Ce(IV). The rate of the disappearance of ceric ions was found to be inversely proportional to [M] 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 HSO₄^?, SO₄^{? ?}, or CIO₄^?, but they are accelerated on the addition of Mn(II) ions. Interpretations of the above observations are furnished.     

Kinetics of interfacial radical polymerization initiated by a glucose-oxidase mediated redox system

The reaction and coating kinetics for the glucose oxidase initiated interfacial polymerization are elaborated. The interfacial film grows rapidly and linearly with time, producing time-dependent controllable conformal coating thicknesses of up to a millimeter in less than 4?min. Bulk polymerization was only observed when the immersing media was stirred to induce higher mass transport rates. The dramatically different film thicknesses observed between different concentrations of glucose in the hydrogel and iron in the bulk media are demonstrated to be a result of an initial rapid growth phase following which the film grows at the same rate nearly independent of either the glucose or iron concentration. The polymerization rate and hence the thickness growth rate in this initial phase saturate at glucose and iron concentrations above 0.8?M and 0.63?mM, respectively. At iron concentrations above 0.05?mM, the film thickness at the end of 3?h of reaction monotonically decreased with increasing iron concentration from 5.7?mm to 4.2?mm. The glucose oxidase is trapped by the growing polymerization front and can be used as the sole enzymatic precursor to coat a second polymeric layer. However, the rate of film growth of the second layer is 14-fold lower than the rate of film growth when bulk enzyme is present during the second stage coating process.     

Radical polymerization and block copolymerization initiated with ceric salt/aldehyde redox system

Aldehyde compounds exhibit very high reactivities towards ceric salt in initiating polymerization of acrylamide. In the presence of aldehyde compounds, the rate of polymerization is 8 times as high as the rate initiated by ceric salt alone. In nitric acid solution, the rate of polymerization decreases, but the accelerating effect of aldehyde compound becomes more obvious. Polyether prepolymer with aldehyde and groups also shows high activity towards ceric salt, with a relative rate of polymerization up to ca. 15, which can initiate acrylamide polymerization to form a block copolymer. The polymerization of acrylonitrile and methyl methacrylate initiated with ceric salt/aldehyde were also investigated.     

Aqueous polymerisation of acrylonitrile initiated by the V(V)-ethylene glycol redox system

The kinetics of acrylonitrile polymerisation initiated by the redox system V(V)-ethylene glycol were investigated in aqueous sulfuric acid in the temperature range 40–50°C. The rate of polymerisation, of V(V) disappearance, and the chain lengths of polyacrylonitrile were measured. The effect of certain water miscible organic solvents and certain neutral salts on the rate of polymerisation was investigated. The kinetics are consistent with the formation of an intermediate complex between the diol and the oxidant whose decomposition leads to the initiating radical. A suitable kinetic scheme is proposed and the various rate and energy parameters are computed.     

Polymerization initiated by the redox system hydrogensulfite/oxygen, 1. Polymerization of acrylic acid

The polymerization of acrylic acid in water by the redox initiation system hydrogensulfite/oxygen was found to proceed fast to give oligomers in high yield, in spite of introducing a large amount of oxygen known as a strong radical inhibitor. In the polymerization system, the concentration of oxygen was kept at a very low level on account of the rapid reaction of hydrogensulfite with oxygen. At high concentration of hydrogensulfite, both hydrogensulfite oxidation rate (R_ox) and polymerization rate (R_p) vary with the flow rate of air. R_p is proportional to the square root of R_ox, suggesting that the termination is a bimolecular reaction, a radical intermediate formed from hydrogensulfite oxidation being the initiator of this polymerization system. Hydrogen was found to behave as a chain transfer agent, and its chain transfer constant is 0,15 at pH 6,9 and 25°C.     

Redox polymerization, 3. Kinetics of acrylonitrile polymerization initiated by the redox systems cyanoacetic acid/Mn(III) and 2-butanone/Mn(III) in aqueous sulfuric acid

The kinetics of Polymerization of acrylonitrile initiated by the redox systems cyanoacetic acid/Mn(III) and 2-butanone/Mn(III) were investigated in the temperature range of 30 – 50°C in aqueous sulfuric acid. The kinetics are consistent with the formation of a 1 : 1 complex between the reducing agent and Mn(III), its unimolecular decomposition yielding the initiating radical. Extensive oxidation of the primary radical with exclusively mutual termination of growing radicals accounts for the kinetics of the polymerization. Rate and equilibrium constants as well as thermodynamic parameters were evaluated and their significance is discussed.     

Vinyl polymerization initiated by the dimethylaniline N-oxide/tosyl chloride system

A study of the vinyl polymerization initiated by the system dimethylaniline N-oxide (DMAO) in conjunction with tosyl chloride (TsCl) has been performed. According to the kinetic results of the polymerization of methyl methacrylate (MMA) and of the copolymerization of MMA with styrene, the polymerization proceeds via a radical mechanism. The rate of polymerization is given by the following equation: and the overall activation energy was calculated to be 14.3 kcal · mole^?1. According to the UV spectrum, the poly-MMA obtained probably contains N-methylanilinomethyl end groups. A graft polymer was obtained by polymerization of MMA with DMAO and partially chlorosulfonated polyethylene (Hypalon-30). From the results an initiation mechanism is proposed and discussed.     

Redox polymerization kinetics of vinyl polymerization initiated by the v5 +/cyclohexanone system in aqueous sulphuric acid

Kinetics of the vinyl polymerization of acrylonitrile initiated by the redox system cyclohexanone/V^{5 +} were investigated in aqueous sulphuric acid in the temperature range of 35—50°C and the rates of polymerization and of V^{5 +} disappearance etc. were measured. From the result it was concluded that the polymerization reaction is initiated by an organic free radical arising from the V^{5 +}-cyclohexanone reaction and terminated by V^{5 +} ions. A suitable kinetic scheme was proposed and the various rate and energy parameters were evaluated.     

Studies on the aqueous polymerization of acrylamide by the acidified potassium permanganate-thioglycolic acid redox system

The polymerization of acrylamide in aqueous media, initiated by the acidified potassium permanganate/thioglycolic acid ( 1 ) redox pair was studied at 30±0,1°C in an inert atmosphere of dry and oxygen-free nitrogen. The initial rate of polymerization was found to be proportional to nearly the first power of potassium permanganate concentration within the range of 2,0.10^?3 to 6,0.10^?3 moll^?1. The rate was also found to be proportional to the first power of [acrylamide] in the range of 8,0.10^?2 to 10,0.10^?2 moll^?1. The rate of polymerization appears to be independent of thioglycolic acid ( 1 ) concentration in the range of 1,0.10^?2 to 1,2.10^?2moll^?1. At still higher concentrations, however, the amount of 1 depresses the rate and maximum conversion. An excess of sulphuric acid was found to affect the rate of polymerization to a slight extent and a deficiency of the acid makes the reaction to stop at an early stage, during the range studied. This indicates, therefore, the presence of an optimum concentration of H₂SO₄ for the smooth initiation of polymerization. A study on the effect of salts reveals that KCl and NH₄Cl lower the initial rate of polymerization, whereas the reverse is true for MnSO₄.H₂O and Na₂C₂O₄. The water-miscible aliphatic alcohols e.g. CH₃OH, C₂H₅OH, (CH₃)₂CHOH, and C₄H₉OH were found to depress the extent of polymerization.     

The initiation mechanism of polymerization by the system AlEt3/H2O

The reaction between H₂O and triethylaluminum Al(Et₃) as well as the initiation mechanism of the polymerization by the system AlEt₃/H₂O have been examined by means of tritiated water, Considerable amount of tritium from tritiated water remained in the system AlEt₃/H₂O prepared at room temperature. Heat treatment of the system causes both the extensive decrease of tritium content and loss of catalyst activity. Polymers of styrene and isobutyl vinyl ether prepared by the system AlEt₃/H₂O were found to be radioactive. These findings have been taken to assume that acid hydrogen does exist in the system AlEt₃/H₂O and is directly responsible for the initiation of cationic polymerization.     

Redox polymerization, 4. Kinetics of the polymerization of acrylic acid derivatives initiated by the system cyanoacetic acid/Mn(OCOCH3)3 in dimethylformamide

The kinetics of the polymerization of acrylonitrile, methyl methacrylate, and acrylamide initiated by the redox system cyanoacetic acid/manganese triacetate in dimethylformamide solution were investigated in the temperature range of 25 – 40°C. It was found that an initial complexation between the reactants followed by an electron transfer yields radicals. In contrast to acrylamide, acrylonitrile and methyl methacrylate effectively suppress further oxidation of the primary radicals. Exclusively the mutual termination accounts for the kinetics of these polymerizations. Data on the average degrees of the polymerizations support the suggested mechanisms. Rate and equilibrium constants were evaluated and their significance is discussed.     

Studies on the mechanism of redox polymerization initiated by N-haloamines and iron(II)

The mechanism of the redox polymerization of methyl methacrylate in aqueous medium in the dark was studied for the redox initiator systems N-halodiethylamine + Fe(II) and triethylamine + halogen + Fe(II), by analysis of the polymer end groups using the dye partition method. In the case of chlorine, both these initiator systems incorporate only the amino group into the polymer to an extent of about one group per polymer molecule. The polymers are found to be free from chlorine. Furthermore, a large portion of the total amino groups introduced into the polymer, using the initiator system triethylamine + halogen + Fe(II) are quaternary in nature. In the case of bromine, both the initiator systems introduce only a bromine atom and no amino group into the polymer. The initiator systems containing chlorine prove to be useful for the preparation of polymers containing amino groups at the one end only.