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.     

Laccase-catalyzed polymerization of acrylamide

Enzymatic polymerization of acrylamide was carried out in water. Laccase, a copper-containing oxidoreductase derived from Pycnoporus coccineus, induced the polymerization at relatively low temperature (50°C) to give a polymer of high molecular weight. In the presence of 2,4-pentanedione, laccase efficiently mediated the vinyl polymerization at room temperature.     

Aqueous polymerization of acrylamide

The polymerization of acrylamide (I) initiated by a potassium bromate—thioglycollic acid (TGA) redox pair has been studied in aqueous media at 30°C in a nitrogen atmosphere. The reaction order related to the catalyst concentration (KBrO₃) was 0.501, which indicated a bimolecular mechanism for the termination reaction in the range of 1.0?3.0 × 10^?3 mole/liter. The polymerization rate varied linearly with monomer (I) concentration over the range of 1.0?5.0 × 10^?2 mole/liter. A typical behavior is observed, however, by changing the thioglycollic acid concentration. The initial rate of polymerization (Ri), as well as the maximum conversion, increases by increasing the temperature to 30°C, but the initial rate and the maximum conversion falls as the temperature rises above 30°C. The overall energy of activation is 6.218 kcal in the temperature range of 20–40°C. Water-miscible organic solvents, namely, CH₃OH and C₂H₅OH, depress the rate of polymerization.     

Kinetic study of the polymerization of acrylamide in inverse microemulsion

The polymerization of acrylamide in inverse microemulsions stabilized by Aerosol OT emulsifier and initiated with azobisisobutyronitrile (AIBN) or potassium persulfate (K₂S₂O₈) has been investigated. The inverse polyacrylamide latexes formed are clear and highly stable. A dilatometric technique was used to follow the conversion of monomer at T = 45°C. The rate of polymerization is first order with respect to initial monomer concentration in the presence of AIBN, and is 1.5 order with K₂S₂O₈. An inverse relationship between molecular weight and emulsifier concentration is found which suggests participation of the emulsifier in the initiation reaction. This is confirmed by the independence of the molecular weight of polyacrylamide on the concentration of the initiators. High values of the rate of polymerization are obtained combined with high molecular weights (up to 10⁷). An important and novel feature of this microemulsion process is that each final latex particle consists of one single molecule of polyacrylamide in a collapsed state. This suggests kinetics which do not follow the Smith and Ewart theory but are characterized by continuous particle nucleation.     

Inverse suspension polymerization of acrylamide

The polymerization of acrylamide in inverse suspension is described and compared with polymerization in solution. The influences of various factors upon the molecular weight of the polymer were studied, viz. the concentration of initiator, the procedure of aqueous phase addition, the nature and concentration of emulsifier, the salt concentration, the time between mixing of phases and start of polymerization etc. Conductometry, NMR and electron microscopy were employed in order to establish the reaction stages and the characteristics of the polymers. The results indicate the importance of each factor and lead to an understanding of the polymerization.     

Electrochemical and chemical polymerization of acrylamide

The electrochemical and chemical polymerization of acrylamide (AA) has been studied. The electrolysis of the monomer in N,N-dimethylformamide (DMF) containing (C₄H₉)₄NClO₄ as the supporting electrolyte leads to polymer formation in both anode and cathode compartments. The cathodic polymer dissolves in the reaction mixture and the anodic polymer precipitates during the course of polymerization. A plausible mechanism for the anodic and cathodic initiation reaction has been given. The chemical polymerization of acrylamide that has been initiated by HClO₄ is analogous to its anodic polymerization. The polymer yield increases with an increase in concentration of the monomer and HClO₄. Raising the reaction temperature also enhances the polymerization rate. The overall apparent activation energy of the polymerization was determined to be ca. 19 kcal/mole. The copolymerization of acrylamide was carried out with methyl methacrylate (MMA) in a solution of HClO₄ in DMF. The reactivity ratios are r₁ (AA) = 0.25 and r₂ = 2.50. The polymerization with HClO₄ appears to be by a free radical mechanism. When the polymerization of acrylamide is carried out with HClO₄ in H₂O, a crosslinked water-insoluble gel formation takes place.     

Permanganate/glycine-initiated polymerization of acrylamide

The kinetics of aqueous polymerization of acrylamide with KMnO₄/glycine redox pair was studied in an atmosphere of nitrogen at 35 ± 0.2°C. The rate of polymerization was found to be first power on monomer, activator, and catalyst concentration. The overall energy of activation was calculated to be 15.66 kcal/deg mol (65.54 kJ/mol) between 30 and 50°C. The effects of various additives (alcohols, neutral salts, complexing agents, addition of catalyst) were studied. The dependence of the polymerization rate on the activator and catalyst concentration was studied in DMF-water mixture also. The molecular weight of polymer was determined at various temperatures of the reaction medium.     

Spontaneous polymerization of acrylamide in glycerol

The spontaneous polymerization of acrylamide in glycerol in the range of 250–350°C has been first observed and investigated. It has been shown that the polymerization proceeds during dissolution of acrylamide in glycerol and leads to formation of gel globules in which the growth of polymer chains takes place. The reaction occurs without termination of kinetic chains in the living polymerization mode. The effective chain transfer at a low concentration of active centers ensures a high yield of the polymer.     

Pulsed laser polymerization study of the propagation kinetics of acrylamide in water

Pulsed laser polymerization was used in conjunction with aqueous‐phase size exclusion chromatography with multi‐angle laser light scattering detection to determine the propagation rate coefficient (k_p) for the water‐soluble monomer acrylamide. The influence of the monomer concentration was investigated from 0.3 to 2.8 M, and k_p decreased with increasing monomer concentration. These data and data for acrylic acid in water were consistent with this decrease being caused by the depletion of the monomer concentration by dimer formation in water. Two photoinitiators, uranyl nitrate and 2,2′‐azobis(2‐amidinopropane) (V‐50), were used; k_p was dependent on their concentrations. The concentration dependence of k_p was ascribed to a combination of solvent effects arising from association (thermodynamic effects) and changes in the free energy of activation (effects of the solvent on the structure of the reactant and transition state). Arrhenius parameters for k_p (M^?1 s^?1) = 10^7.2 exp(?13.4 kJ mol^?1/RT) and k_p (M^?1 s^?1) = 10^7.1 exp(?12.9 kJ mol^?1/RT) were obtained for 0.002 M uranyl nitrate and V‐50, respectively, with a monomer concentration of 0.32 M. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1357–1368, 2005     

Mechanistic aspects of group transfer polymerization

The experimental evidence supporting the involvement of enolate anions in group transfer polymerization(GTP) is reviewed. The results of silyl group exchange studies between living silyl ketene acetal-ended oligomers under typical GTP conditions are discussed. It is concluded that the observations of significant amounts of silyl group exchange in the presence of polymerizing monomer are not consistent with the originally proposed “associative mechanism” based on the GTP Criterion which precludes intermolecular silyl group exchange.     

A calorimetric study of spontaneous polymerization in acrylamide systems containing metal nitrates

A calorimetric study of the kinetics of spontaneous polymerization of acrylamide in systems containing Cr(III) and Er(III) nitrates has been carried out. At 20–25 °C, the process is characterized by a considerable induction period (20–40 min), a fast increase of the polymerization rate, up to its maximum value (5–10 min), and its subsequent slow decrease to insignificant values. It has been established that the composition of the reaction mixture significantly affects the recorded polymerization rates, and practically does not change the time parameters and the integral degrees of conversion of the process, which are 20 and 80 % for the nitrates of Cr(III) and Er(III), respectively. The effect of the addition of water or inhibitors of radical reactions on the process has been studied.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1070–1074, June, 1993.     

A study on acrylamide polymerization by anodic contact glow-discharge electrolysis: A novel tool

Contact glow-discharge electrolysis (CGDE) is an unconventional electrolytic phenomenon in which a plasma is sustained by a direct current (dc) glow-discharge between an electrode and the liquid electrolyte around it. A remarkable feature of CGDE is highly nonfaradaic chemical effects at the glow-discharge electrode. During anodic CGDE of an aqueous electrolyte, non-Faradaic yields originate mainly from reactions triggered by H^• and OH^• radicals generated in high local concentrations near the anodic plasma/liquid electrolyte interface during the process. The radical-generating potentiality of anodic CGDE was explored for the polymerization of acrylamide in aqueous media. The percentage of monomer conversion, rate of polymerization, charge efficiency, and viscometric average molar mass of the polymers produced were measured as functions of the quantities of electricity passed. The charge efficiency of the polymerization of acrylamide by anodic CGDE was at least 1 order of magnitude higher than that of ordinary electrochemically initiated polymerization. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1584–1588, 2001     

Kinetics of the dispersion polymerization of acrylamide

Aqueous solutions of acrylamide were dispersed with non-ionic surfactants within isoparafinic hydrocarbons to particles of approx. 1 μm and polymerized in a batch reactor by water-soluble and oil-soluble azo-initiators at 42 to 57°C. The resulting conversion-time curves are S-shaped showing a strong gel effect. For maximum rate of polymerization, the following kinetic expressions were determined for the conditions investigated:

$\text{r}{}_{\mathrm{<mtext>max</mtext>}}\text{=kC}{}_{\mathrm{<mtext>I,o</mtext>}}{}^{0.5}\text{C}{}_{\mathrm{<mtext>M,o</mtext>}}$

for water-soluble initiators;

${}_{\mathrm{<mtext>max</mtext>}}\text{=kC}{}_{\mathrm{<mtext>I,o</mtext>}}\text{C}{}_{\mathrm{<mtext>E,o</mtext>}}{}^{\mathrm{?0.2}}$

For oil-soluble initiators, the overall rate constant k is a function of interface area and temperature. The interface area is dependent on the phase ratio, stirring speed and temperature. For constant interface areas, an activation energy of 26 kJ/mol was found. The overall activation energy of the polymerization is 88.2 kJ/mol, when temperature dependence of the interphase is not taken into account. Polymerization of acrylamide with oil-soluble initiators can be described at low conversions by a model which considers mass transfer of primary radicals, and to a lesser extent of initiator molecules, from the oil phase into the water phase as rate determining step and termination by primary radicals. The resulting molecular weights of the polymer are extremely high (10⁶g/mol) and depend on temperature, stirring speed and concentration of initiator, emulsifier and monomer.     

Electroinitiated polymerization of acrylamide in acetonitrile medium

The electroinitiated polymerization of acrylamide (AA) has been studied in acetonitrile medium using tetrabutylammonium perchlorate (TBAP) as the electrolyte. Split-cell experiments showed that the polymer formation takes place both in the anode and the cathode compartments. The polymer yield depends on several factors such as the magnitude of the current flow, the duration of the electrolysis, the monomer concentration, the electrolyte concentration, the temperature of the solution, presence or absence of air, and finally whether or not the cell content was stirred. The current exponent of the polymerization was 0.28 with a reaction rate constant of 1.06 reaction % per hour. The IR and NMR spectra of the polymers suggest that the anodic polymer is polyacrylamide and the cathodic polymer is poly-β-alanine (? CH₂? CH₂? CO? NH? ). Based on the experimental results, a radical mechanism for the anodic polymerization and an anionic mechanism for the cathodic polymerization have been proposed.