Aqueous Polymerization Of Acrylamide Research Articles

Synthesis of a polyacrylamide hydrogel modified with a reactive carbamate surfactant: Characterization, swelling behavior, and mathematical models

Hydrogels are polymeric materials that can absorb and retain large amounts of water. They have various applications in agriculture, horticulture, oil recovery, and water management. However, conventional hydrogels have limited swelling (Q), equilibrium swelling (Q∞), and water retention capacities (DQ) under different environmental conditions. In this study, we synthesized a series of hydrophobically associated hydrogels by the aqueous polymerization of acrylamide, acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid, and a novel amphiphilic hydrophobic monomer (RCS-10). Further, we investigated the effects of the RCS-10 content on Q, the mechanical properties, and water retention capacity (DQ) of the hydrogels. We also examined the influence of temperature, pH, salt type and concentration, and urea concentration on Q, finding that an increase in the RCS-10 content decreased Q and increased the DQ of the hydrogels. The hydrogels exhibited high Q in distilled water, low-salt solutions, and low-urea (1 wt%) solutions. In the latter, the Q∞ was as high as 768.99 g/g. The hydrogels also showed excellent cyclic swelling performance and maintained high Q∞ (759.99 g/g) after six cycles. Crucially, the hydrophobic association hydrogels demonstrated superior swelling and water retention properties compared to conventional hydrogels. Thus, the hydrogels have applications in water management in various fields including agriculture and horticulture.

Solar–Thermal Conversion Properties of Bilayered Porous Solar Absorbers Fabricated by Mixed Halloysite/Palygorskite Clays

In recent years, solar absorbers have received widespread attention, however, large‐scale preparation is difficult to achieve for many absorbers, and the raw materials are expensive. Halloysite (HNTs) and palygorskite (PAL) have the advantage of abundant reserves and low prices. Herein, solar absorbers with bilayer and porous features are prepared from mixed clays of HNTs and PAL; further studies focused on the solar–thermal conversion efficiency of the absorbers. The mixed clays are gelated by aqueous polymerization of acrylamide and N, N′‐methylene bisacrylamide, then the surface of the gel is carbonized to obtain the double‐layer solar absorbers (F‐HNTs/PAL). The F‐HNTs/PAL shows excellent thermal stability with a weight‐loss ratio of 13% at 1,000 °C, good mechanical properties with a compressed strength of up to 200 KPa at 80% strain, abundant porosity with an adsorption pore volume of 0.057 cm3 g−1, and low thermal conductivity (0.206 W m−1 K−1). Under 1 sun illumination, the F‐HNTs/PAL has a higher vapor rate of 1.215 kg m−2 h−1 that equals 84% solar‐to‐vapor efficiency, which is much more than 57% of F‐HNTs prepared by the same methods, but the F‐HNTs/PAL shows unique thermal stability and mechanical property.

Cathodic Aqueous Polymerization of Acrylamide with ZnCl2

The electroinitiated polymerization has been described here. The polymerization mixture consisted of monomer dissolved in an aqueous solution of ZnCl2, and was subjected to electrolysis in a divided cell. The rates of polymerization increased linearly with increase in applied current level and monomer concentration. Polymers of high molecular weights (≍105) were obtained from intrinsic viscosity measurements that increased with monomer concentration. The cyclic voltammogram of acrylamide in H2O -ZnCl2 solution suggests that the monomer gets directly reduced at cathode and the polymerization mechanism is anoinic.

Sorptive removal of methylene blue from aqueous solutions by polymer/activated charcoal composites

AbstractIn this study, a new sorbent, a poly(acrylamide‐co‐itaconic acid) [P(AAm‐co‐IA)]/activated charcoal (AC) composite, was prepared by the aqueous polymerization of acrylamide and itaconic acid in the presence of AC with N,N′‐methylene bisacrylamide as a crosslinker and potassium persulfate as an initiator. The P(AAm‐co‐IA)/AC composite sorbent showed a fair capacity to adsorb the cationic dye methylene blue. The maximum sorption capacity, as studied at 23, 37, and 50°C and determined with the Langmuir isotherm model, was found to be 909.0, 312.5, and 192.3 mg/g, respectively. For an initial concentration of 5 mg/L, the kinetic uptake data were studied with various kinetic models. The pseudo‐second‐order equation was found to fairly fit the uptake data with a regression value of 0.999. The dye uptake increased with the pH of the sorbate solution, and the optimum pH was found to be in the range of 7–10. Intraparticle diffusion was also observed to take place, and the coefficient of intraparticle diffusion was evaluated to be 26.51 × 10−2 mg g−1 min−1/2. The various thermodynamic parameters were also determined to predict the nature of the uptake process. The sorption process was found to be spontaneous, as indicated by a negative standard free energy change. The negative standard enthalpy change suggested an exothermic nature for the uptake. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Chemical Polymerization of Acrylamide Initiated with Ce(IV)-Dicarboxylic Acid Redox System: Effect of Chain Length Between the Carboxyl Groups

Aqueous polymerization of acrylamide (AAm) was carried out with the Ce(IV)-dicarboxylic acid initiator system. Dicarboxylic acids with numbers of methylene groups ranging from 1 to 7 were used to elucidate the effect of chain length between the carboxyl groups on the formation of polymer, which is reflected in yield and molecular weight of polymer. The end group analysis of polyacrylamides was carried out by using conductometric titration. The number average molecular weight results from end group analysis are compared with values from viscometric analysis.

Polymerization of acrylamide and methacrylamide initiated by a potassium peroxydiphosphate/Mn(II) system

The kinetics of aqueous polymerization of acrylamide (AM) and methacrylamide (MAM) have been studied using a potassium peroxydiphosphate (PDP/Mn(II) system in an inert atmosphere at 40°C and at constant pH (1.30). The polymerization rate R p has been found to be proportional to the half power of PDP and Mn(II) concentrations. The overall energy of activation (ΔE) was found to be 40.2 ± 0.1 kJ mol -1 and 45.0 ± 0.1 kJ mol -1 for AM and MAM, respectively. Intrinsic viscosity [η], viscometric average molecular weight (M v ) and number average degree of polymerization (P n ) at different concentrations of PDP, Mn(II) and monomer are reported.

Aqueous polymerization of acrylamide by electrolitically generated KMnO4 organic acid redox systems

Polymerization of acrylamide was carried out with potassium permanganate–malonic acid, potassium permanganate–tartaric acid, and potassium permanganate–citric acid redox initiator systems with and without electrolysis. The effect of potassium permanganate concentration, acrylamide concentration, and temperature on the polymerization yield was studied and molecular weights of polymers were determined and compared with electrolytic conditions. At low concentrations of potassium permanganate, continuously supplying Mn(III) has an advantage over the noneelectrolytic method for which polymerization did not occur under these conditions. © 1996 John Wiley & Sons, Inc.

Initiation Mechanism of Radical Polymerization Using Ammonium Persulfate and Polymerizable Amine Redox Initiators

Abstract A redox initiation system consisting of a polymerizable amine such as N-[(3-dimethylamino)-propyl] acrylamide(DMAPAA) or N-[(3-dimethylamino)-propyl] methacrylamide(DMAPMA) and ammonium persulfate(APS) used for aqueous polymerization of acrylamide(AAM) has been studied. It has been found that the rate equation of AAM polymerization is in good agreement with the redox initiated polymerization rate equation, and the overall activation energies of the polymerization obtained are 35.04 and 40.96 kJ/mol for APS/DMAPAA and APS/DMAPMA systems, respectively. Accordingly, the systems belong to redox ones. The initiation mechanism of the polymerizable redox systems has been investigated by means of electron paramagnetic resonance(EPR), Fourier-transform infrared(FT-IR) and ultra violet(UV) spectroscopies. Two kinds of radicals, alkylamino methyl radical and monomeric propagating radical have been detected by EPR spectroscopy. Based on experimental results the initiation mechanism of ammonium persulfate/pol...

Polymerization Initiated by the System Triethanolamine/Hydrogen Sulfite with and Without the Cooperation of Hydrogen Peroxide. 1. Polymerization of Acrylamide

Abstract Attempts to initiate the aqueous polymerization of acrylamide, AAm, by the hydrogen sulfite/oxygen system failed. This is contrary to acrylic acid, whose monomer indeed undergoes initiation by the above initiator. Efforts to start the AAm polyreaction by hydrogen sulfite without air also yielded no polymer. It was discovered, however, that sodium pyrosulfite, PS, coupled with triethanolamine, TEA, in equimolar ratios provides a system, TEA/PS, able to generate radicals even at relatively low temperatures. On the basis of ESR investigations, these proved to be HSO3 active centers. At three temperature (273, 278, 283 K) at an initiator (TEA/PS) molar concentration range of c 1(0) = 0.0066–0.02 mol/dm3, and for a monomer (AAm) concentration range of c M(0) = 0.43–1.374 mol/dm3, high rates of polymerization lying between r p = 24.9 × 10−6 and 727.5 × 10−6 mol/dm3·s were determined. Linear relationships between lg(r p) vs lg(c 1(0)) at constant c M(0), and lg(r p) vs lg(c M(0)), at constant c 1(0) dis...

Aqueous polymerization of acrylamide initiated by cerium(IV)-nitrilotriacetic acid redox initiator

Nitrilotriacetic acid (NTA) coupled with commonly used metal oxidants was used as an initiator for the aqueous polymerization of acrylamide (AM) under neutral or acidic conditions. The cerium(IV)-NTA pair under neutral conditions behaved as the most promising redox initiator. In order to find the mechanism of generation of free radicals and to determine the complex formation constant ( K) and the disproportionation constant ( k d), blank tests for the reactions of Ce(IV) with NTA were conducted under conditions of neutral, 1 N HNO 3 and 1 N NaNO 3, respectively. The mechanism was further confirmed by 13C and 1H n.m.r. spectra and the kinetic parameters for the aqueous polymerization of AM were evaluated. The effects of additives on the polymerization were studied and the use of the Ce(IV)-NTA redox pair for other aqueous polymerization systems such as acrylic acid (AA), acrylonitrile (AN) and methyl methacrylate (MMA) was also studied.

A New Redox Initiating System for the Polymerization of Vinyl Monomers

Abstract A new redox system, dioxane-ascorbic acid, has been investigated for the homopolymerization of vinyl monomers. Detailed kinetic studies on the aqueous polymerization of acrylamide by this initiating system have been done iodometrically at 35 ± 0.2°C. The effect of various additives, such as organic solvents, inorganic salts, surfactants, etc., on the rate of polymerization has been studied. The retardation constants for organic solvents have been evaluated by the “intercept method.” The overall energy of activation has been found to be 8.75 kcal/deg/mol, within the temperature range 25–45°C. A suitable mechanism has been suggested. The following rate expression: Rp α [acrylamide]1.0 [dioxane]1.0 [ascorbic acid]0, has been observed.

Aqueous polymerization of acrylamide initiated by 4,4′-azobis (4-cyano pentanol) and chain extension of polyacrylamide by means of ceric ion redox systems

The polymerization of acrylamide (AA) initiated by 4,4′-azobis (4 cyanopentanol) (ACP) was investigated in aqueous solution at 60°C. The molecular weight and the conversion depend on polymerization duration and initiator concentration. Polymerization of AA initiated by ACP yields polyacrylamide (PAA) with hydroxyl terminal groups. Redox polymerization of AA initiated by hydroxyl terminated PAA in conjuction with Ce(IV) provided increase in the molecular weight of the initial polymer.

Aqueous solution polymerization of acrylamide at low conversions: 1. Kinetics and transfer studies

The aqueous polymerization of acrylamide, initiated by 4,4'-azobis-4-cyanovaleric acid, has been studied in the presence of propionamide, and oligoacrylamide, at 30–90°C. Molecular weights were determined viscometrically and transfer constants to propionamide, oligoacrylamide and monomer were evaluated. Exponents expressing the dependency of initial polymerization rate on monomer and initiator concentrations at 50°C were 1.16±0.01 and 0.52±0.03, respectively.

Polymerization of Acrylamide Initiated by the Redox System Potassium Persulfate/Lactic Acid, Catalyzed by Silver Ions

Abstract The aqueous polymerization of acrylamide initiated by the potassium persulfate/lactic acid system catalyzed by Ag+ ions has been studied iodometrically over the temperature range from 35 to 50 ± 0.2°C. The rate of polymerization is governed by the expression Rp ∞ [M]0.8[K2S2O8]1.0[Ag]1.0 The deviation from normal kinetics has been studied. A tentative mechanism of initiation is suggested. The overall energy of activation is 5.52 kcal/mol.

Permanganate/L-Cysteine Initiated Polymerization of Acrylamide

Abstract The kinetics of aqueous polymerization of acrylamide with KmnO4L-cysteine redox system has been studied in an atmosphere of nitrogen at 35 ± 0.2°C. The rate of polymerization has been found to be first power on monomer concentration, 0.5 power with respect to catalyst, and first power with respect to the activator concentration. The overall energy of activation has been calculated to be 11.3 kcal/deg′mol between 30 and 50°C. The effects of various additives (alcohols, neutral salts, complexing agents, surfactants) have also been studied.

Aqueous Polymerization of Acrylamide Initiated by Glycolic Acid/Ce4+Redox System

Abstract The aqueous polymerization of acrylamide initiated by the glycolic acid/Ce4+ redox system was studied in sulfuric acid medium at 35 ± 0.2°C under a nitrogen atmosphere. The initiation was carried out by the free radical generated in the decomposition of the complex formed between the oxidant and the reductant. The monomer disappearance was found to be proportional to [GA]0,89[Ce4+]0.57[M]1.0, and the rate of ceric ion disappearance was found to be directly proportional to [Ce4+] and [GA] but independent of [M]. The activation energy of the system was found to be 7.21 kcal/deg/mol. The molecular weight of polyacrylamide increased with increasing [monomer] and decreased with increasing [catalyst]. The effect of pH was also studied in the pH range 2.22 to 1.44.

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

AbstractThe 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

Abstract 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.

Aqueous polymerization of acrylamide initiated by Ce(IV)-thiomalic acid redox system

The use of a Ce (IV)-thiomalic acid (Ce4+-TMA) redox system as an initiator in the polymerization of acrylamide (M) in an aqueous medium has been investigated. The Ce4+ forms a 1∶1 complex with TMA, decomposing through free radical mechanism in an acid medium. From 5 to 15% conversion the rate equation is \(R_p = - \frac{{d[M]}}{{dt}} = k[M]^{3/2} [Ce^{4 + } ]^x [TMA]\) where Rp is the rate of polymerization and x is 0.5 or 1.0 depending upon the concentration of monomer. The overall energy of activation has been calculated to be 9.12 k cal. deg−1 mol−1(38.12 kJ/mol) in the investigated range of temperature (25°–40°C) the degree of polymerization (P) of the polymer is directly proportional to [M]. The number of average molecular weight of the polymer remains unaffected at lower concentration of Ce4+ and is found to decrease at higher concentrations.

Estimation of transfer constants in the aqueous solution polymerization of acrylamide with potassium persulfate initiator

An experimental investigation on the aqueous polymerization of acrylamide with potassium persulfate initiator is reported. Molecular weight averages were measured by viscometry. Non-Newtonian effects were accounted for by extrapolation to high shear rates where the polymer solutions approximated Newtonian behavior. Values for the transfer constants to the acrylamide monomer and to the persulfate initiator were estimated at 25 and 40°C and compared to literature values.