Radiation (60Co)-Induced Graft Copolymerization of Acrylamide on Jute Fiber

The radiation induced graft copolymerization of acrylamide onto jute fibers was studied following preirradiation of jute in air using a⁶⁰Co source of γ-radiation and subsequent polymerization of acrylamide in a limited aqueous system under nitrogen at 607°C. An increase of the time of preirradiation (at a fixed dose rate) increased the percent grafting measurably and the grafting efficiency marginall Grafting effects showed further improvement on addition of Fe²⁺ or Co²⁺ ions to the system prior to the polymerization step. Increasing the concentration of Fe²⁺ or Co²⁺ ion led to an increase in the grafting parameters with a leveling off effect in the higher concentration range, however. An increase in the polymer (jute) content for a fixed monomer content produced a significant increase in the efficiency of grafting, while % grafting followed a slowly decreasing trend.     

Grafting onto wool. III. Graft copolymerization of poly(vinyl acetate) by use of fenton's reagent as initiator

In an attempt to modify fibrous protein, poly(vinyl acetate) has been graft copolymerized onto Himachali wool in an aqueous medium by using Fenton's reagent as redox initiator. Graft copolymerizations were carried out at 25, 30, 35, 40, and 45°C for a period of 3 hr. Percentage grafting was found to be dependent upon reaction temperature, concentration of monomers, and the molar ratio of [H₂O₂]/[Fe⁺²]. Maximum grafting occurred at 45°C with a molar ratio of [H₂O₂]/[Fe⁺²] = 1.43. A small amount of grafting (2.6–2.8%) occurred when grafting was effected at 45°C in the presence of Fe⁺² alone.     

Aqueous polymerization of methacrylamide

The aqueous polymerization of methacrylamide (I) initiated by KBrO₃–thioglycolic acid (TGA) has been studied at 30 ± 0.2°C in nitrogen. The rate is given by K[M]^1.19 [thioglycolic acid]¹ [KBrO₃]^0.53 for 10–15% conversion. Activation energy was found to be 53.96 kJ/mole (12.92 kcal/mole) in the investigated range of temperature 30–45°C. The role of addition of a series of aliphatic alcohols and some salts was also determined. The kinetics of polymerization was followed iodometrically.     

Radiation-induced grafting in the polyethylene–styrene system and differential thermal analysis of the grafted samples

The graft polymerization of styrene onto high-density polyethylene films was carried out by γ-irradiation in the vapor phase. Two methods were used for grafting in these experiments: a preirradiation method and a simultaneous irradiation method. The effects of these grafting methods on the reaction mechanism of grafting and on the properties of the grafted samples were investigated. The amounts of styrene homopolymer in the grafted samples is under 2% in the case of the preirradiation method and above 10% in the case of the simultaneous irradiation method. The activation energies were calculated to be 18 kcal/mole for grafting in the preirradiation method and 15 kcal/mole for weight increase of polyethylene films in styrene vapor. The difference in the dimensional expansion between in the direction of stretching and the direction prependicular to it is smaller with preirradiation grafting than with grafting by the simultaneous irradiation method. Differential thermal analysis of the grafted films shows an endothermic peak due thermal decomposition which decreases gradually from 450°C to 415°C with increase in degree of grafting from 30 to 60%. The lowering of this peak temperature appears at a lower degree of grafting when the preirradiation method is used. On the basis of these results, it is concluded that the reaction rate of radiation-induced grafting in the vapor phase depends closely upon the processes of adsorption, dissolution, and diffusion of styrene monomer in polyethylene films; in the case of simultaneous irradiation method, the reaction proceeds comparatively uniformly in the amorphous region, while in the case of the preirradiation method, the reaction proceeds mainly at the boundary of the crystalline and amorphous regions.     

Oxygen promoted radical polymerization of acrylonitrile in aqueous nitric acid. A kinetic study

The polymerization of acrylonitrile (AN) initiated by oxygen-ascorbic acid (AA)-ferric ion system was studied in dil. HNO₃ at 40°. The rate of polymerization, R_p, was found gravimetrically. In the [Fe³⁺] range, (2–5 × 10^?5 M, R_p was proportional to [AN]^{1.5 ± 0.05}, [O₂]^{0.5 ± 0.02} [AA]⁰ and [Fe³⁺]⁰; for [Fe³⁺] = (5–30) × 10^?5 M, it was proportional to [AN]^{1.8 ± 0.05}, [O₂]^{0.6 ± 0.02}, [AA]⁰ and [Fe³⁺]^{?0.9 ± 0.05}. A plausible reaction scheme is proposed and rate law presented to explain these results. R_p increased with ionic strength and [HNO₃] (up to ～0.25 M). An initial rate increase with temperature followed by a decrease was noticed. Chain lengths of the polymers were determined viscometrically.     

Kinetics and mechanism of the reduction of μ-adi-di[N,N′-bis{salicylideneethylenediaminatoiron(III)}] by dithionate ion

The kinetics and mechanism of the reduction of the μ-adi-di[N,N′-bis{salicylideneethylenediaminatoiron(III)}] complex, [Fe₂adi], by dithionate ion, S₂O₆ ^2?, have been investigated in aqueous perchloric acid at 29 °C, I = 0.05 mol dm^?3 (NaClO₄) and [H⁺] = 5.0 × 10^?3 mol dm^?3. Spectrophotometric titrations indicated that one mole of the reductant was oxidized per mole of oxidant. Kinetic profiles indicated first-order rate with respect to [Fe₂adi] but zeroth-order dependence on [S₂O₆ ^2?]. The rate of reaction increased with increase in [H⁺], decreased with increased dielectric constant, but was invariant to changes in ionic strength of the medium. Addition of small amounts of AcO^? and Mg²⁺ ions did not catalyse the reaction. A least-squares fit of rate against [H⁺]² was linear (r ² = 0.984) without intercept. The reaction was analysed on the basis of a proton-coupled outer-sphere electron transfer mechanism.     

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.     

Complexation kinetics of Fe2+ with 1,10‐phenanthroline forming ferroin in acidic solutions

The formation kinetics of ferroin is studied under varied acid conditions at 25°C and fixed ionic strength (0.48 mol dm^?3) under pseudo‐first‐order conditions with respect to Fe²⁺ by using the stopped‐flow technique. The reaction followed is first and third order with respect to Fe²⁺ and 1,10‐phenanthroline (phen)_T, respectively. Increasing the acid concentration retarded the reaction, and the reaction rate showed a positive salt effect. The rate‐limiting step involved the complexation of the phen or protonated phen with [Fe(phen)₂]²⁺ complex ion, leading to formation of [Fe(phen)₃]²⁺ ion. The observed retardation of the reaction rate with increasing [H⁺]₀ is due to the increased [phenH⁺]_eq and low reactivity of phenH⁺ with [Fe(phen)₂]²⁺ complex ion. Simulated curves for the acid variation experiments agreed well with the corresponding experimental curves and the estimated rate coefficients supporting the proposed mechanism. Relatively low energy of activation (26 kJ mol^?1) and high negative entropy of activation (?159.8 J K^?1 mol^?1) agree with the proposed mechanism and the formation of compact octahedral complex ion. © 2008 Wiley Periodicals, Inc. 40: 515–523, 2008     

Electrochemical Study on Decomposition of Hydrogen Peroxide with Fe(II)

Decomposition of H₂O₂ with Fe²⁺ was studied with SnO₂ electrodes. By chronoamperometric and voltammetric techniques, the diffusion coefficients of Fe^3* and H ₂O₂ were estimated to be 5 × 10-₆ and 2 × 10^?5 cm²/s, respectively; the rate of decomposition of H₂O₂ with Fe²⁺ was proportional to [H₂O₂]^1/2·[Fe²⁺]² at a smaller concentration of Fe²⁺, but to [H₂O₂]^1/2·[Fe²⁺] when [Fe²⁺] was increased, indicating the formation of ferryl ion and the electron exchange between it and Fe²⁺ playing important roles. This catalytic decomposition. was dependent on pH; the maximum rate was observed to occur about pH = 1.5.     

Substitution inertness of [Ir(H2O)6]3+

Ligand substitution properties of the recently characterized pale-yellow [Ir(H₂O)₆]³⁺ ion in perchlorate solutions, have been investigated. At 120°C in sealed tubes observations on the exchange with H₂¹⁸O are impaired by a spurious oxidation to purple Ir(IV). Over extended periods at 40°C the ion has been shown to be extremely inert, and the rate constants for substitution of Cl⁻ into [Ir(H₂O)₆]³⁺ is estimated to be < 2 × 10⁻⁹ M⁻¹ S⁻¹.     

Kinetic Study of the Reduction of Bromate Ion by Tris(1,10-Phenanthroline)Iron(II) and Aquoiron(II) Ions — Implication for the Bromate-Gallic Acid Oscillating Reaction

The kinetics of the bromate oxidation of tris(1,10-phenanthroline)iron(II) (Fe(phen)₃²⁺) and aquoiron(II) (Fe²⁺ (aq)) have been studied in aqueous sulfuric acid solutions at μ = 1.0M and with Fe(II) complexes in great excess. The rate laws for both reactions generally can be described as -d [Fe(II)]/6dt = d[Br^?]/dt = k[Fe(II)] [BrO^?₃] for [H⁺]₀ = 0.428–1.00M. For [BrO^?₃]₀ = 1.00 × 10^?4M. [Fe²⁺]₀ = (0.724–1.45)x 10^?2 M, and [H⁺]₀ = 1.00M, k = 3.34 ± 0.37 M^?1s^?1 at 25°. For [BrO^?₃]₀ = (1.00–1.50) × 10^?4M, [Fe²⁺]₀ = 7.24 × 10^?3M ([phen]₀ = 0.0353M), and [H⁺]₀ = 1.00M, k = (4.40 ± 0.16) × 10^?2 M^?1s^?1 at 25°. Kinetic results suggest that the BrO^?₃-Fe²⁺ reaction proceeds by an inner-sphere mechanism while the BrO^?₃-Fe(phen)₃²⁺ reaction by a dissociative mechanism. The implication of these results for the bromate-gallic acid and other bromate oscillators is also presented.     

Grafting vinyl monomers onto silk fibers. IX. Graft copolymerization of methyl methacrylate onto silk using peroxydiphosphate-thiourea redox system

The graft copolymerization of methyl methacrylate (MMA) onto silk in aqueous media initiated by the potassium peroxydiphosphate-thiourea redox system was studied at 50°C. The rate of grafting was determined by changing [monomerl], [thiourea], [initiator], acidity of the medium, reaction medium, and temperature. A significant increase percent of grafting was noticed with increasing monomer concentration to 84.49 × 10^?2 mole/liter and the further increase is associated with the decrease of graft yield. The graft yield increases with an increase of thiourea (Tu) concentration to 25 × 10^?5 mole/liter; then it decreases. A measurable increase in graft yield was observed with an increase in acidity of the medium. Graft yield increases to a certain temperature, i.e., 50°C, and then it decreases. The graft yield increases with an increase of initiator concentration to 60 × 10^?4 mole/liter; then it decreases. The graft yield is medium dependent. A suitable kinetic path has been proposed and the rate equation has been derived.     

[Mn(H_2P_2O_7)_3]~(3-)引发淀粉与丙烯腈接枝聚合反应的动力学研究

以[Mn(H_2P_2O_7)_3]~(3-)为引发剂,研究了丙烯腈与玉米淀粉的接枝共聚反应。由实验结果求出了反应速率与引发剂浓度、单体浓度、淀粉浓度和反应温度的关系,推导并验证了接枝反应动力学模型,探讨了反应机理,求得了接枝反应活化能。     

Graft copolymerization of methyl methacrylate onto lignosulfonate by H2O2–Fe(II) redox system. I. Preparation and characterization of the graft copolymer

Graft copolymerization of methyl methacrylate onto lignosulfonate in aqueous medium was investigated. It was found that the H₂O₂–Fe(II) redox system is very effective for the grafting (E_a = 4.4 kcal/mole). The H₂O₂/Fe²⁺ ratio was the most important factor in the graft copolymerization and characteristics of the resultant graft copolymers. In most cases, polymerization for 100 min at 30°C was enough to obtain 80% conversion and 50–60% grafting efficiency. The resultant polymer mixture was subjected to extraction alternately with acetone and water, and the graft copolymer was isolated free from homopolymer and unreacted lignosulfonate. With increasing H₂O₂/Fe²⁺ ratio, the grafting ratio showed a maximum at 4, whereas the yield of graft copolymer and number of poly(methyl methacrylate) branches for every building unit of lignosulfonate increased up to a ratio of 4, both values, however, remaining constant above 4. The graft copolymer obtained for the case H₂O₂/Fe²⁺ = 4 consisted of one part of lignosulfonate and five parts of poly(methyl methacrylate). The number of branches in the graft copolymer was 6 × 10^?3/OCH³ or one every 167 guaiacyl nuclei.     

Polymerization of Acrylonitrile Initiated by 1,4-Dimethyl-1,4-bis(p-nitrophenyl)-2-tetrazene

The polymerization of acrylonitrile (AN) initiated by 1,4-dimethyl-1,4-bis(p-nitrophenyl)-2-tetrazene (Ie) was studied in dimethylformamide (DMF) at high temperature. The polymerization proceeds by a radical mechanism. The rate of polymerization is proportional to [Ie]^0.64 and [AN]^1.36. The overall activation energy for the polymerization is 21.5 kcal/mole within the temperature range of 115-130°C. The chain transfer of Ie was also undertaken over the temperature range of 120-135°C. The activation parameters for the decomposition of Ie at 120°C are k_d = 2.78 × 10^?6 sec^?1, ΔH^? = 40.8 kcal/mole, and ΔS^? = 19.5 cal/mole-deg, respectively.     

Aqueous polymerization of acrylamide by persulphate/thiolactic acid initiator system

The aqueous polymerization of acrylamide initiated by ammonium persulphate/thiolactic acid has been studied at 35 ± 0.2° in nitrogen. The rate is given by k[M]^1.4 [thiolactic acid]^0.24 [ammonium persulphate]^x, where x is nearly 0.5 and 1.0 at concentrations 0.15 mole l^?1 and 0.05 mole l^?1 of monomer respectively. The deviations from normal kinetics are discussed. The overall activation energy is 7.96 kcal mole^?1.     

Initiation of polymerization of methyl methacrylate by oxalic acid and iron(III) mixtures

The polymerization of methyl methacrylate either by free radical or charge transfer mechanism has been studied in dimethyl sulphoxide at 60° in the presence of oxalic acid and hexakis dimethylsulphoxide iron(III) perchlorate, [Fe(DMSO)₆](ClO₄)₃. Increased rate was noticed for 1:1 mole ratio of oxalic acid to Fe³⁺ for charge transfer polymerization; a well defined induction period was found for free radical polymerization in the same systems. Mechanisms for the two types of reaction are proposed. The rate constant for the interaction of poly(methyl methacrylate) radical with the iron-oxalate complex was found to be 1.52 × 10⁵ l. mol^?1 sec^?1 at 60°.     

Polymerization of Methacrylamide Initiated by Ceric Ion-Citric Acid Redox System

Homogeneous polymerization of methacrylamide initiated by the ceric ammonium sulfate-citric acid (CA) redox pair has been investigated and reported at 35 ± 0.2°C under nitrogen atmosphere. The initiation was caused by the free radical generated by the decomposition of the complex formed between ceric ion and citric acid. The rate of monomer disappearance was found to be proportional to [CA]^0.4, [Ce^0.4+]^0.65, and [Monomer]¹ The rate of ceric ion disappearance was directly proportional to the ceric ion concentration but independent of the monomer concentration. The initial rate was independent of [H₂SO₄]. The activation energy of the system was found to be 21.4 kJ/mol.     

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

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.     

Ceric Ion Initiated Graft Polymerization onto Poly(vinyl Alcohol)

This paper describes the kinetics of the ceric ion-initiated graft co-polymerization of vinyl acetate-acrylonitrile to poly(vinyl alcohol). The graft copolymerization rate R_p was found to be first order with respect to the total concentration of the comonomer mixture [M], the concentration of vinyl alcohol repeating units [PVA], and the mole fraction of vinyl acetate in the comonomer feed mixture. R_p was independent of cerous ion. The grafting rate was independent of ceric ion above a ceric concentration of 0.0020 M but first order in ceric ion below that concentration. Rp initially increased rapidly with [H⁺] to a maximum and then decreased and levelled off at hgher [H⁺]. The rate of ceric ion disappearance was first order in [PVA], independent of [MI, and increased with increasing [H⁺] with a leveling off at high [H⁺]. A reaction mechanism.