Kinetics of nitrogen dioxide initiated polymerization of acrylamide

The polymerization of acrylamide initiated by NO₂ in DMF was investigated. The initial rate of the polymerization increases with the first power of the monomer concentration and a half power of the initiator concentration. The overall activation energy of the polymerization was determined to be about 20 kcal/mol (84 kJ/mol). The copolymerization of acrylamide was also carried out with MMA in a solution of NO₂ in DMF. The copolymer was found to be enriched in MMA content. The polymerization appeared to be initiated by free radicals.     

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.     

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.     

Kinetics of polymerization of tetrahydrofuran initiated by acetyl perchlorate

The kinetics of the polymerization of tetrahydrofuran by acetyl perchlorate in methylene chloride solution was studied, and the results were compared with those previously reported by using perchloric acid/acetic anhydride as catalyst. The initiation and propagation mechanisms are discussed by taking into account the influence of the counterion. The initiation reaction takes place instantaneously, but the propagation proceeds by macroesters and macroions and the contribution of macroester to propagation is much lower than the contribution of macroions.     

Redox polymerization, 7. Kinetics of the polymerization of acrylic acid derivatives initiated by the systems cyanoacetic acid/Mn(OCOCH3)3 and ethyl acetoacetate/Mn(OCOCH3)3 in glacial acetic acid

The kinetics of polymerization of acrylamide, acrylonitrile and methyl methacrylate by the systems cyanoacetic acid/Mn(OCOCH₃)₃ as well as ethyl acetoacetate/Mn(OCOCH₃)₃ were investigated in glacial acetic acid medium in the temperature range of 25–45°C. Oxidation proceeds through intermediate complex formation between reactants. Competitive complexation of the substrates by Mn(II) leads to retadation of the rates by added manganous ions. Primary radicals from the substrate account for the initiation when acrylamide is used as the monomer, but with acrylonitrile and methyl methacrylate secondary radicals formed by the interaction of the 1:1 complex with monomers account for initiation. In presence of the monomers the retardation due to added manganous ions is absent. Termination in all cases is of the mutual type. Rate and equilibrium constants were evaluated.     

Investigation of the polymerization of octanelactam initiated with hydrochloric acid

The polymerization of octanelactame ( 1 ) initiated by HCl takes place according to the characteristic kinetic curves. Both characteristics, i.e., the fast initial and the extremely slow further stages, and the kinetic anomaly (in certain cases under otherwise identical conditions less polymer is formed at higher than at lower temperatures) can be interpreted easily on the basis of a mechanism already suggested by the authors. The two relevant chain growth reactions, i.e., lactam addition on \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm R}\mathop {\rm N}\limits^ \oplus {\rm H}_{\rm 3} $\end{document}-groups and the reaction between \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm R}\mathop {\rm N}\limits^ \oplus {\rm H}_{\rm 3} $\end{document} and N-acylamide groups, proceed through a tetrahedral intermediate in two directions, one of them being the known chain growth, the other one an amidine (or acylamidine) formation, in which the active groups, ensuring chain growth, desactivate. Both kinetic characteristics could be interpreted on the basis of the suggested mechanism, by measuring the amounts of amino and amidine groups with the progress of polymerization.     

Kinetics of the early stages of high‐energy radiation initiated polymerization

We describe our method based on pulse radiolysis with optical detection developed for the examination of the kinetics and mechanism of the first steps of high‐energy radiation initiated polymerization. The absorption spectra of the intermediates were obtained in cyclohexane solution of hexanediol diacrylate (HDDA) of different concentrations. In dilute solution (10 mmol·dm^–3) and short time (10 μs) after the pulse, the spectrum of the monomer radicals was observed. On increasing the monomer concentration, the maximum of the spectrum was shifted to longer wavelength indicating the start of the oligomerization reaction. The increase in the time of observation resulted in a similar shift in dilute solution. From the kinetic curves the rate coefficients of termination for the monomer radicals (2·k_t,m) and average rate coefficients of termination for the oligomer radicals of different chain length (2·k_t) were determined. The average rate coefficient of termination was found to decrease in time (that is with increasing chain‐length).     

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.     

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.     

Kinetics of deactivation in the BuOTiCl3/AlEt2Cl initiated polymerization of styrene

The deactivation of the catalytic activity of the BuOTiCl₃/AlEt₂Cl initiated polymerization of styrene in heptane was found to follow a second-order rate law. The varying slopes in the second-order plots observed with varying catalyst concentrations are due to the heterogeneous nature of these colloidally dispersed catalysts. Site poisoning by reversible adsorption of the AlEtCl₂ formed, is proposed as the probable reason for the deactivation.     

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.     

Kinetics of radical polymerization of methyl methacrylate initiated with dimethyl 2,2′-azodiisobutyrate

The kinetics of free-radical bulk polymerization of methyl methacrylate with dimethyl 2,2′-azodiisobutyrate as an initiator was investigated at 40, 60, and 80°C. Non-ideal polymerization behaviour was observed when the initiator concentration was varied by a factor of more than one thousand. This departure from classical polymerization kinetics is discussed in terms of primary radical termination and a chain length dependent termination rate constant, with the structural similarity of both primary and polymeric radicals facilitating the treatment very much. The kinetic analysis indicates that in the polymerization of methyl methacrylate the termination rate constant is a function of the degree of polymerization of the involved macroradicals.     

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.     

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.     

Polymerisation of trioxane, 2. Kinetics of the reaction initiated by chlorosulphonic acid

The kinetics of polymerisation of trioxane, initiated by chlorosulphonic acid have been studied in o-dichlorobenzene, trichloroethylene, and carbon tetrachloride. The reaction is shown to be simple, though the kinetics are different in the above solvents. With very pure and dry substrates, no induction period is observed. Rate parameters have been evaluated.     

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.     

Electrochemically initiated bulk polymerization of trioxane

The electroinitiated bulk polymerization of trioxane containing tetrabutylammonium perchlorate as background electrolyte has been investigated at the temperature of 66,5°C. The polymerization can be started by a very small charge initially supplied and does not present significant termination features. The resulting polymers have high molecular weights, which are dependent on the current amounts, and show satisfactory thermal stability. The species initiating the polymerization is perchloric acid, which is produced by anodic oxidation of the perchlorate ion, followed by hydrogen atom abstraction from trioxane. Bulk trioxane polymerizations catalyzed by added perchloric acid, show in fact similar features as to kinetic chain length, molecular weight of the polymers and polymerization rate, with respect to the electroinitiated trioxane polymerizations.     

Thermally initiated emulsion polymerization of styrene

The thermal polymerization of styrene in emulsion was studied by determination of the number of particles, the rate of polymerization, and the average molecular weight of the polymer formed as a function of the emulsifier concentration. For the number of particles the relation N ～ [E]^1,4 was found, whereas the rate of polymerization showed a dependence of v_br ～ [E]^0,7, only up to an emulsifier content of 0,2 mol. dm^?3, but remained constant at higher concentrations. A transfer of low molecular weight radical species from the organic to the aqueous phase is discussed as a prerequisite of polymerization in the latex particles. The deviations from the Smith-Ewart theory are explained by the low rate of radical formation, which does not provide a constant radical concentration per particle.