Kinetics of retarded polymerization: Investigation of the retardation of V5+–thiourea initiated polymerization of methyl acrylate by phenol

The kinetics and mechanism of the retarding action of phenol on the V⁵⁺–thiourea initiated polymerization of methyl acrylate (MA) have been studied within the temperature range of 30–50°C. The effects of retarder (phenol), metal ion (V⁵⁺), monomer (MA), sulfuric acid, some organic solvents and inorganic salts on the percentage and rate of polymerization have been studied. The remarkable observation of the present study is the positive intercept obtained from the plot of [M]/R_p vs. 1/[M]. This type of observation is significantly different from previous studies on retarded polymerization. The values of composite rate constants k₀k_t/k_ik_pkK have been calculated from plots of [M]/R_p vs. 1/[M]. On the basis of experimental findings a reaction mechanism has been suggested, and a suitable rate expression has been proposed and explained.     

Determination of kinetic parameters and potential residence of phenol degradation on C-felt electrode

The electrooxidation of phenol has been studied on C-felt electrode by using cyclic voltammetry (CV) technique. The kinetic parameters electrooxidation reaction such as oxidation potential at zero scan rate (E ₀), temperature coefficient (dE/dt), reaction order (n), activation energy (E _a), calculated from variation of oxidation peak potentials and current with potential scan rate, phenol concentration and related temperature. Phenol reaction path way (either degradation or polymerization and forming high molecular weight species) and potential residence of phenol degradation are determined by applying different electrolysis voltage values (0.630, 1, 2 and 3 V) in acidic phenol solution (0.0125 M Phenol + 0.5 M H₂SO₄). In addition, decrease in the phenol concentration is monitored in this solution during 6 hours with 1 hour time period and from this data linear relation ship was found to between applied potential and phenol removal efficiency. Published in Russian in Elektrokhimiya, 2009, Vol. 45, No. 3, pp. 281–288. The article is published in the original.     

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

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 R_p ∞ [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.     

Radical polymerization of new functional monomer: Methacryloyl isocyanate containing 4‐chloro‐1‐phenol

New functional monomer methacryloyl isocyanate containing 4‐chloro‐1‐phenol (CPHMAI) was prepared on reaction of methacryloyl isocyanate (MAI) with 4‐chloro‐1‐phenol (CPH) at low temperature and was characterized with IR, ¹H, and ¹³C‐NMR spectra. Radical polymerization of CPHMAI was studied in terms of the rate of polymerization, solvent effect, copolymerization, and thermal properties. The rate of polymerization of CPHMAI has been found to be smaller than that of styrene under the same conditions. Polar solvents such as dimethylsulfoxide (DMSO) and N,N‐dimethyl formamide (DMF) were found to slow the polymerization. Copolymerization of CPHMAI (M₁) with styrene (M₂) in tetrahydrofuran (THF) was studied at 60°C. The monomer reactivity ratio was calculated to be r₁ = 0.49 and r₂ = 0.66 according to the method of Fineman—Ross. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 469–473, 2000     

Polymerization of Acrylonitrile Initiated by the Redox System,K2S2O8-Citric Acid Catalyzed by Silver Ion

The polymerization of acrylonitrile initiated by the redox system K₂S₂O₈-citric acid catalyzed by Ag⁺ ion has been studied over the temperature range 35–50°C. The rate of polymerization is proportional to the square root of peroxydisulfate concentration. The initial rate increases with increasing citric acid concentration, but at relatively higher concentration of citric acid the rate decreases. The rate of polymerization also increases with increasing monomer concentration and temperature. The overall activation energy calculated from the Arrhenius plot was found to be 4.6 kcal/mole. On the basis of the observation, a suitable kinetic scheme has been proposed for the reaction.     

Polymerization of methyl acrylate mediated by copper(0)/Me6‐TREN in hydrophobic media enhanced by phenols; Single electron transfer‐living radical polymerization

Phenol has been used as an additive to enhance the rate of SET‐LRP in toluene at ambient temperature. A direct relationship between reaction time and amount of phenol added has been found with the optimum amount being ～ 20 equiv. of phenol with respect to initiator. Polymerization of methyl acrylate (MA) has been carried out in the presence of varying amounts of phenol and the rate of polymerization depends on the concentration of phenol relative to initiator. With a 20‐fold excess 93% conversion is observed after 218 min (PDI = 1.06, M_n = 11,500 g mol^?1) when compared with 80% conversion with a 5‐fold excess (PDI = 1.21, M_n = 5310 g mol^?1). When nonsterically hindered phenols are employed in a 20 molar excess with respect to the initiator the polymerizations have good linear first‐order kinetics and give polymers with PDI between 1.06 and 1.16. When a highly hindered phenol is employed there is a significant induction period prior to polymerization taking place which is similar to when using no phenol. Less hindered phenols accelerated the polymerization when compared with polymerizations with no added phenol. Increasing steric hindrance at the ? OH prevents this coordination which indicates that the role of phenol is different with either copper(0) or copper(I). Aliphatic and aromatic esters and amides were used successfully as initiators giving polymers with M_n close to that predicted at ～ 10,000 g mol^?1 and PDI typically less than 1.10. An induction period is observed in most cases which can be removed by a pre‐equilibrium step before the addition of monomer. This results in excellent first‐order kinetics being observed in the polymerization of MA in toluene solution (50 vol %). Here Cu(0) (powder)/Me₆‐TREN with 20 equiv. of phenol and all of the reactants, except the monomer, were added to the reaction flask and stirred for 45 min at 25 °C. The structure of the polymer is shown by MALDI TOF MS to contain bromide chain ends derived from the alkyl bromide initiator. The retention of this end group is consistent with living radical polymerization. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7376–7385, 2008     

Polymerization of tetrafluoroethylene initiated by fluorinated petroleum coke

The polymerization of tetrafluoroethylene initiated by the inorganic polymer fluorocarbon material CF_0.95 prepared by the high-temperature fluorination of petroleum coke has been studied. The kinetics of the process has been examined, and the dependences of the rate of polymerization and the yield of polymer on monomer pressure and temperature have been considered. The free-radical mechanism of the process is established by ESR. The kinetic features of initiation and polymerization leading to an exponential growth in rate in the initial non-steady-state portion of kinetic curves are discussed.     

Role of heterogeneous Cr(AcAc)3–AlEt3 catalyst system in isoprene polymerization

Polymerization of isoprene in presence of a heterogeneous Ziegler-type catalyst system, Cr(AcAc)₃–AlEt₃, has been studied in benzene medium. The rate of polymerization is first-order with respect to catalyst as well as monomer concentration. The rate studies, activation energy, and polymer microstructures are reported in order to follow the probable mechanism of polymerization.     

二价锰盐存在下过硫酸钾引发丙烯酰胺聚合反应的研究

<正> 用过硫酸钾(以下用KPS表示)或三价锰盐单独作为引发剂,或者高价锰盐和过硫酸钾分别与另一还原剂组成氧化-还原引发体系,以引发单体丙烯酰胺(以下用AM表示)聚合,已有许多报道。为了弄清用KPS引发AM聚合时二价锰盐的影响,本文用膨胀计法研究了二价锰盐存在下,KPS引发AM聚合的动力学(用膨胀计毛细管内液柱     

Effect of valence state of vanadium on stereoblock polymerization of methyl methacrylate with VOCl3–AlEt2Br catalyst system

The polymerization of methyl methacrylate with the VOCL₃–ALEt₂Br catalyst system in n-hexane has been studied. The first-order dependence of rate of polymerization on catalyst and monomer concentrations, activation energy of 6.67 kcal/mole, and NMR spectra of polymer lend support to a coordinate anionic mechanism of polymerization. It has been shown that the vanadium in V⁺² oxidation state is less active than V⁺³ oxidation state of active complex.     

Donor–acceptor interactions in cationic polymerization. VII. Relationship between the degree of dissociation of complex and the molecular weight of polyisobutylene formed in the presence of some complexes of aluminum trichloride with electron donors

The concentration dependence of the specific conductivity of the complexes of aluminum trichloride with dibutyl ether, anisole, phenol, and diphenyl ether at equimolar ratios of the two compounds has been measured. Conductivity measurements have been carried out in ethyl chloride at ?78.5°C. Except for dibutyl ether, all the complexes studied are associated over the whole concentration range and their degree of dissociation and molar conductivity are independent of the concentration. In the case of the BuOBu·AlCl₃ complex these quantities begin to be independent of the concentration only at concentrations higher than 20 mmoles/l. The degree of polymerization or the molecular weight of polyisobutylene formed by the polymerization in the presence of given complexes is inversely proportional to the concentration of the anions present. This is especially evident from the fact that the relation between x and 1/M? is also linear in the case of the BuOBu·AlCl₃ complex, whose degree of dissociation and therefore molar conductivity varies distinctly with the concentration of the complex. The comparison of the chain-breaking efficiency of the anions derived from phenol and diphenyl ether with those derived from phenetole and anisole shows that the mixed aryl alkyl ethers split after reacting with aluminum trichloride under these conditions, so that the phenyl group becomes a part of the cation and the alkyl group a part of the anion. On the basis of the different behaviors of the ions and the dipoles, the differences in the dependence of the degree of polymerization on the dielectric constant of the medium in the cationic polymerization have been explained.     

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.     

Polymerization of Pu(IV) in aqueous nitric acid solutions

The polymerization of Pu(IV) in aqueous nitric acid solutions has been studied spectrophotometrically both to determine the effects of large UO₂(NO₃)₂ concentrations on the polymerization rates and, more generally, to review the influence of other major parameters on the polymer reaction. Typically, experiments have been performed at 50°C and at 0.05M Pu in aqueous solutions of HNO₃ at concentrations ranging from 0.07 to 0.4M. An induction period usually precedes the polymer growth stage, during which time it is believed that primary hydrolysis products form and begin to aggregate. Uranyl nitrate retards the polymerization reaction by approximately 35% despite the counteracting influence of the nitrate ions associated with this solute. The rate of polymer formation at 50°C has been shown to be third order in Pu(IV) concentration.     

Effect of Glycerol in the Polymerization of Methyl Methacrylate by Mn(III) Acetate

The kinetics of the mechanism of the polymerization of methyl methacrylate initiated by the glycerol/Mn(III) acetate redox system has been investigated in aqueous sulfuric acid medium in the temperature range of 40 to 50 °C. The effects of glycerol, methyl methacrylate, metal ion, acetic acid, and sulfuric acid on the rates of polymerization have been studied. One striking observation is that the increase in monomer concentration steadily decreases the rate of polymerization, contrary to what was observed in the case of acrylonitrile. On the basis of these observations, an appropriate kinetic scheme and rate expression have been developed.     

Kinetics of the potassium persulfate-initiated inverse emulsion polymerization of sodium acrylate solutions

The kinetics of the K₂S₂O₈-initiated inverse emulsion polymerization of aqueous sodium acrylate solutions in kerosene with Span 80 as the emulsifier has been studied. The conversion-time curves are S-shaped. The following expressions have been obtained for the maximum rate of polymerization and the molecular weight of the polymers under the experimental conditions investigated: R_max ∞ [K₂S₂O₈]^0.78[sodium acrylate]^1.5[Span 80]^0.1, (OVERLINE)M(/OVERLINE)_u ∞ [K₂S₂O₈]^−0.37[sodium acrylate]^2.9[Span 80]^−0.2. The activation energy for the maximum rate of polymerization is 94.8 kJ mol^−1. The results suggest a monomer–droplet–nucleation mechanism for the system studied. © 1996 John Wiley & Sons, Inc.     

Ruthenium(III) catalysis in polymerization of vinyl monomers by charge‐transfer mechanism with aminoalcohols and carbontetrachloride: A kinetic study

The kinetics of ruthenium(III) catalyzed polymerization of vinyl monomers (M) (methyl‐, ethyl‐, and butylacrylates) by charge‐transfer mechanism with aminoalcohols (AA) (namely, ethanol‐, diethanol‐, and triethanol amines) and carbontetrachloride in dimethylsulfoxide medium have been studied. The rate of polymerization depends on the [CCl₄]/[AA] ratio and may be represented as and The rate of polymerization of monomers with each aminoalcohol was found to be in the order R_p (methyl‐)> R_p (ethyl‐)> R_p (butylacrylate) while that of each monomer with different aminoalcohols was found to be in the order of R_p tertiary > R_p secondary > R_p primary aminoalcohol. The suitable mechanism for the polymerization process consistent with kinetic data has been proposed. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 585–592, 2006     

Solid-state initiation of polymerization of N-vinylcarbazole by gases

Chlorine gas has been shown by previous investigators to initiate the polymerization of solid N-vinylcarbazole at room temperature, giving a maximum yield of 66% polymer after 18 hr. This initiation of polymerization of N-vinylcarbazole without the application of heat, by a gas, is the only solid-state initiation other than those that are radiation-induced known to us. This study was undertaken in order to determine both the scope and the mechanism of the room-temperature solid-state initiation of vinyl polymerization of N-vinylcarbazole by gases. The gases (HCl, Cl₂, and N₂O₄) were absorbed by solid N-vinylcarbazole, giving very rapid exothermic polymerization: HCl, 37% polymer yield, M?_n 2500; Cl₂, 50% polymer yield, M?_n 4703; N₂O₄, 91% polymer yield, M?_n 7073. The gases NOCl, BF₃, and HBr were not absorbed by N-vinylcarbazole and did not initiate polymerization. The N₂O₄-initiated polymerization, which gave a high yield of polymer, was complete within 5 min. after introduction of gas. This polymerization method and the resulting polymer compared favorably with conventional peroxide-initiated melt polymerization and the polymer obtained thereform. The mechanism of gas-initiated polymerization, which was studied with introduction of inhibitors, appears to be classically cationic in nature.     

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.     

表面活性单体AMC14AB在水溶液中的聚合动力学研究

采用溴酸钾-溴化钾法研究了阳离子型表面活性单体(2-丙烯酰胺基)乙基十四烷基二甲基溴化铵(AMC14AB)在水溶液中的聚合动力学,分别考察了引发剂浓度与单体浓度对聚合速率的影响,确定了聚合速率方程,分析了聚合机理,考察了温度对聚合反应的影响,测定了聚合表观活化能。研究结果表明,由于AMC14AB在水溶液中的胶束化行为,使其具有较快的聚合速率,于60℃下聚合,40min内转化率即可达到80%以上;AMC14AB的聚合速率方程为Rp=k[M]0.92[I]0.48,说明链终止为双基终止方式,引发过程与单体无关;聚合表观活化能为80.72kJ/mol。     

Asymmetric chain-growth synthesis of polyisocyanide with chiral nickel precatalysts

Nickel(II)-aryl complexes [(L₂)Ni(Ar)Br] bearing either chiral phosphine ligands (L₂ = RR- or SS-DIPAMP, Ar = ortho-anisyl), or a chiral aryl-group have been prepared, and their structural optical an chiroptical properties have been characterized. Enantiomeric pairs of both catalysts have been used for the asymmetric polymerization of different isocyanides ( M1 , M2 , M3 ), to give well defined polyisocyanides ( P1 , P2 , P3 ). Their polymerization behavior has been studied, which confirmed chain-growth polymerization in all cases. The asymmetric induction has been verified by circular dichroism spectroscopy on enantiomeric pairs of all three polymers.