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.     

On some regularities of grafting of vinylpyridine derivatives onto acetyle cellulose

The radical graft copolymerization of vinylpyridine derivatives onto acetyl cellulose was investigated using Fe²⁺/H₂O₂ redox system as an initiator. It was proved that the addition of hydrazine hydrate increased the degree of grafting many times. The reaction mechanism of hydrazine hydrate was also investigated. A. correlation between nitrogen content and the total anion exchange capacity was established. The vinylpyridine derivatives were ordered according to their reactivity. The effects of reaction conditions on the total anion-exchange capacity, the total conversion, the degree of grafting, and the grafting efficiency of the copolymers obtained were examined. The copolymers were characterized by IR and H-NMR spectra, thermogravimetric analysis, elemental analysis, and total anion-exchange capacity.     

Grafting onto chitosan. I. Graft copolymerization of methyl methacrylate onto chitosan with Fenton's reagent (Fe2+−H2O2) as a redox initiator

Poly(methyl methacrylate) has been grafted onto chitosan by using Fenton's reagent as a redox initiator in an aqueous medium. Initiation by Fenton's reagent was carried out in the presence of atmospheric oxygen. The percentages of grafting, efficiency, and homopolymer were found to depend on chitosan (RchitOH), ferrous ammonium sulfate (FAS), hydrogen peroxide, monomer (MMA) concentrations, reaction temperature, and reaction time.     

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.     

A study of the graft copolymerization of methacrylic acid onto starch using the H2O2/Fe++ redox system

Graft copolymerization of methacrylic acid (MetAc) onto potato starch using H₂O₂/Fe⁺⁺ redox system was investigated. The best conditions of the grafting reaction were determined and several variables were studied: initiator and monomer concentrations, time, and temperature. Percent grafting efficiency, percent grafting, percent grafted monomer conversion, and total conversion were obtained. The optimum graft yield was obtained at 7.3 × 10^?3M H₂O₂ concentration and it was favored by increasing the methacrylic acid concentration and reaction time.     

Controlled grafting of MMA onto cellulose and cellulose acetate

Homogeneous graft copolymerization of methyl methacrylate onto cellulose and cellulose acetate was carried out in various solvents and solvent systems taking ceric ammonium nitrate, tin (II) 2-ethyl hexanoate [Sn(Oct)₂] and benzoyl peroxide as initiators. The effect of solvents, initiators, initiator and monomer concentration, on graft yield, grafting efficiency and total conversion of monomer to polymer were studied. Formation of Ce³⁺ ion during grafting in presence of CAN enhances the grafting efficiency. Methylene blue was used as a homopolymer inhibitor and controlled the molecular weight of the grafted polymer and its effect on grafting was also studied. In presence of MB, amount of PMMA homopolymer formation reduced and consequently grafting efficiency increased. The number average molecular weights and polydispersity indices of the grafted PMMA were found out by gel permeation chromatography. The products were characterized by FTIR and ¹H-NMR analyses and possible reaction mechanisms were deduced. Finally, thermal degradation of the grafted products was also studied by thermo-gravimetric and differential thermo-gravimetric analyses.     

Kinetics of aerobic and anaerobic oxidations of ethanol by Fenton's reagent

For the first time, the time dependence of [H₂O₂] and [Fe²⁺] was followed during the aerobic oxidation of ethanol by Fenton's reagent. It was found that part of the ethanol was oxidized by dissolved O₂ via the transient formation of H₂O₂. A model was set up based on FeO²⁺ as the key intermediate. Both one‐ and two‐equivalent oxidations of ethanol occur, the former producing radical species derived from ethanol. No free radicals derived from H₂O₂ play part in the system. The relevant rate constants or their ratios were determined. The mechanism accounted successfully also for the anaerobic oxidation of ethanol. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 541–553, 2008     

Preparation and characterization of a poly(vinylbenzyl sulfonic acid)‐grafted FEP membrane

In this study, a novel polymer electrolyte membrane, poly(vinylbenzyl sulfonic acid)‐grafted poly(tetrafluoroethylene‐co‐hexafluoropropylene) (FEP‐g‐PVBSA), has been successfully prepared by simultaneous irradiation grafting of vinylbenzyl chloride (VBC) monomer onto a FEP film and taking subsequent chemical modification steps to modify the benzyl chloride moiety to the benzyl sulfonic acid moiety. The chemical reactions for the sulfonation were carried out via the formation of thiouronium salt with thiourea, base‐catalyzed hydrolysis for the formation of thiol, and oxidation with hydrogen peroxide. Each chemical conversion process was confirmed by FTIR, elemental analysis, and SEM‐EDX. A chemical stability study performed with Fenton's reagent (3% H₂O₂ solution containing 4 ppm of Fe²⁺) at 70 °C revealed that FEP‐g‐PVBSA has a higher chemical stability than the poly(styrene sulfonic acid)‐grafted membranes (FEP‐g‐PSSA). © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 563–569, 2010     

Chemical Oxidative Degradation of Acridine Orange Dye in Aqueous Solution by Fenton's Reagent

Degradation of acridine orange (AO) in aqueous solution by Fenton's reagent (Fe²⁺ and H₂O₂) was investigated. The effects of different reaction parameters such as initial AO concentration, pH value of solution, ferrous concentration, hydrogen peroxide concentration, and the presence of chloride ion on the oxidative degradation of AO were investigated. Under optimum conditions, 2 mM H₂O₂, 0.4 mM Fe²⁺ and pH 3.0, the initial 0.2 mM AO solution was reduced by 95.8% within 10 min. The primary intermediates of the degradation reaction of AO were identified. The analytical results indicated that the N‐de‐methylation degradation of AO dye took place in a stepwise manner to yield mono‐, di‐, tri‐, and tetra‐N‐de‐methylated AO species generated during the Fenton process. The probable degradation pathways were proposed and discussed.     

On the Modification of Chitosan Through Grafting

Abstract

The feasibility of grafting poly(methyl acrylate) and poly[1-(methoxycarbonyl) ethylene] onto chitosan, poly-β(1←-4)-2-amino-2-deoxy-d-glucose, was investigated. The grafting reaction was carried out in aqueous solution by using ferrous ammonium sulfate (FAS) in combination with H₂O₂ as redox initiator. The effects of such reaction variables as chitosan, monomer and initiator concentrations, reaction time, and reaction temperature were determined. Through this study the grafting reaction could be optimized. The grafting yield reached its maximum value of 332% when 0.3 g chitosan was copolymerized with 3 mL monomer at 70°C for 120 minutes with [FAS] = 6 × 10^?5 M, [H₂O₂] = 6 × 10^?3 M, and 8 mL water. The grafted chitosan was found to be insoluble in solvents for chitosan and solvents for poly(methyl acrylate), but did show swelling in dilute acetic acid, methanol, acetone, and in an ethanol/2% acetic acid 1:1 mixture. The thermal stability of chitosan and grafted chitosan were studied by dynamic thermogravimetric analysis. The results show that the graft copolymer is thermally more stable than pure chitosan. The overall activation energy for graft copolymerization was estimated to be 32.8 kcal/mol.     

Grafting onto wool. XXV. Effect of acids on γ-radiation-induced graft copolymerization of methyl methacrylate onto wool fiber

Graft copolymerization of methyl methacrylate (MMA) onto Himachali wool fiber has been investigated in aqueous medium by using γ irradiation from a 2100 Ci⁶⁰CO source as means of initiation. Graft copolymerization was carried out by the mutual method in nitrogen atmosphere as well as in air. Effect of mineral acids and acetic acid on percentage of grafting was studied. Percentage of grafting was determined as functions of total dose, concentration of monomer, and concentration of acids. Maximum percentage of grafting in the presence of acids occurred in nitrogen atmosphere at a total dose of 1.05 MR. All the acids were found to influence grafting and the reactivity of different acids towards graft copolymerization was found to follow the order: H₂SO₄ > HCl > HNO₃ > HC1O₄ > HOAc. An attempt has been made to explain the reactivity order of different acids in the light of the mechanism proposed for γ-irradiation-induced graft copolymerization of vinyl monomer onto wool fiber.     

Electrocatalytic Reduction of Oxygen at Anthraquinonedisulfonate/Polypyrrole Composite Film Modified Electrodes and Its Application to the Electrochemical Oxidation of Azo Dye

We report here the electrocatalytic reduction of oxygen on thin anthraquindisulfonate (AQDS)/poplypyrrole (PPy) composite film modified electrodes and its application to the electrooxidation of azo dye‐amaranth. The polymer‐coated cathode exhibited good electrocatalytic activity towards oxygen reduction reaction (ORR), and allowed the formation of strong oxidant hydroxyl radical (^.OH) in the medium via Electro‐Fenton's reaction between cathodically generated H₂O₂ and added or regenerated Fe²⁺. The electrochemical behaviors of ORR in various pH solutions were described using cyclic voltammetry (CV), rotating disk electrode (RDE) and chronoamperometric (CA) techniques. The effect of solution pH on amaranth mineralization by the Fe²⁺/H₂O₂ and Fe³⁺/H₂O₂ electrooxidation systems was studied. In addition, the long‐term electrocatalytic activity and stability of the AQDS/PPy composite film during multiple experimental runs were also examined electrochemically.     

Grafting onto Wool. XXVII. Graft Copolymerization of MixeD Vinyl Monomers by Use of Ceric Ammonium Nitrate as Redox Initiator

In order to ascertain the effect of a donor monomer, vinyl acetate (VAc), on the graft copolymerization of acceptor monomers, ethyl acrylate (EA) and butyl acrylate (BA), grafting of mixed vinyl monomers (EA + VAc) and (BA + VAc) was carried out on Himachali wool in aqueous medium using ceric ammonium nitrate (CAN) as a redox initiator. Graft copolymerization was carried out at different temperatures for various reaction periods. Percent grafting and percent efficiency were determined as functions of 1) concentration of mixed vinyl monomers, 2) concentration of CAN, 3) concentration of HNO₃ 4) temperature, and 5) reaction time. VAc, the donor monomer, was found to decrease percent grafting of EA and BA onto wool.     

Effect of stirring on cellulose graft copolymerization. IV. Grafting of styrene by initiator systems involving potassium persulfate

Dissolving pulp and its partially xanthated derivative were grafted with styrene, using either the Fe²⁺?K₂S₂O₈ redox system of potassium persulfate alone as initiators. The conversion of styrene to both copolymer and homopolymer was found to be influenced by agitator speed. The effect of stirring was much more pronounced with the xanthated substrate in that a welldefined conversion maximum was observed at the same agitation speed for both total polymer and copolymer. Grafting onto dissolving pulp with the redox initiator also showed a maximum, but a maximum total polymer and maximum copolymer were located at different agitator speeds. Grafting of styrene onto dissolving pulp initiated by potassium persulfate was almost independent of stirring in the 0–910 rpm range.     

Grafting onto Gelatin. II. Graft Copolymerization of Ethyl Acrylate and Methyl Methacrylate onto Gelatin in the Presence of Ce4+ as Redox Initiator

In order to initiate a comprehensive study of graft copolymerization of vinyl monomers onto soluble protein-gelatin, we have studied grafting of ethyl acrylate (EA) and methyl methacrylate (MMA) onto gelatin using eerie ammonium nitrate (CAN) and eerie ammonium sulfate (CAS) as the redox initiator in an aqueous medium. A small amount of mineral acid (HNO₃ with CAN and H2SO4 with CAS) was found to catalyze the graft copolymerization. Graft copolymerization reactions were carried out at different temperatures. Maximum grafting occurred at 65°C both with EA and MMA. Percentage grafting has been determined as function of 1) concentration of monomer (EA and MMA), 2) concentration of initiator (CAN and CAS), 3) concentration of acid (HNO3 and H2SO4), 4) time, and 5) temperature.     

Grafting onto Wool. XXVI. Graft Copolymerization of Vinyl Monomers by Use of Cr(acac)3-TBHP as Initiator

Methyl methacrylate (MMA), methyl acrylate (MA), and ethyl acrylate (EA) have been graft copolymerized onto wool fiber in aqueous medium using the chromium acetylacetonate-tertiary-butyl hydroperoxide (Cr(acac)₃-TBHP) system as initiator. The percentage of grafting has been determined as a function of the concentrations of monomer, chelate, and TBHP, and the time and temperature under optimum conditions. MMA produced a maximum grafting of 119.8%, MA produced a maximum grafting of 56%, while EA afforded maximum grafting to the extent of 41.9%. Different vinyl monomers were found to follow the following reactivity order toward grafting onto wool fiber in the presence of the Cr(acac)₃-TBHP system: MMA > MA > EA.     

Monomer Protonation‐Dependent Surface Polymerization to Achieve One‐Step Grafting Cross‐Linked Poly(4‐Vinylpyridine) Onto Core–Shell Fe3O4@SiO2 Nanoparticles

Functional polymer‐grafting silica nanoparticles hold great promise in diverse applications such as molecule recognition, drug delivery, and heterogeneous catalysis due to high density and uniform distribution of functional groups and their tunable spatial distance. However, conventional grafting methods from monomers mainly consist of one or more extra surface modification steps and a subsequent surface polymerization step. A monomer protonation‐dependent surface polymerization strategy is proposed to achieve one‐step uniform surface grafting of cross‐linked poly(4‐vinylpyridine) (P4VP) onto core–shell Fe₃O₄@SiO₂ nanostructures. At an approximate pH, partially protonated 4VP sites in aqueous solution can be strongly adsorbed onto deprotonated silanol groups ( Si O⁻) onto Fe₃O₄@SiO₂ nanospheres to ensure prior polymerization of these protonated 4VP sites exclusively onto Fe₃O₄@SiO₂ nanoparticles and subsequent polymerization of other 4VP and divinylbenzene monomers harvested by these protonated 4VP monomers onto Fe₃O₄@SiO₂ nanoparticles, thereby achieving direct grafting of cross‐linked P4VP macromolecules onto Fe₃O₄@SiO₂ nanoparticles.     

Grafting of monodisperse low-molecular-weight polystyrene onto cellulose acetate

Well-defined low-molecular-weight polystyrene was grafted onto cellulose acetate in a homogeneous solution. The grafting was performed by esterifying the free hydroxyls in the cellulose acetate (acetyl DS 2.5) with anionically prepared polystyrene having a carboxylic acid group at one end of the chain. The carboxylic acid end group of the polystyrene was activated by either conversion to the corresponding acid chloride, or by reaction with trifluoroacetic anhydride. Pyridine and the more active 4-dimethylaminopyridine were used as catalysts in the esterifications. The polystyrene contents of the copolymers varied between 10 and 80% and the molecular weights of the polystyrene grafts were 2500, 12,100 and 17,100 (M?_w/M?_n = 1.1).     

The ferric ion catalyzed decomposition of hydrogen peroxide in perchloric acid solution

Predictions of the “redox” and “complex” schemes for the Fe³⁺ catalyzed decomposition of H₂O₂ have been compared with published and new experimental data by numerical integratior of the appropriate complete sets of differential equations. Apparent discrepancies for the redox scheme at high Fe³⁺/H₂O₂ ratios are shown to disappear in the complete treatment, and inconsistencies of the complex scheme with both kinetic data and spectroscopic measurements are pointed out.     

钙钛矿氧化物H1.9K0.3La0.5Bi0.1Ta2O7和Pt/WO3组成的Z体系下完全光解水性能

以质子化层状钙钛矿氧化物H_1.9K_0.3La_0.5Bi_0.1Ta₂O₇ (HKLBT)作为产氢催化剂, Pt/WO₃作为产氧催化材料进行Z 型体系下完全分解水反应. 考察了不同载流子传递介质及不同载流子浓度对反应活性的影响. 结果表明, 以Fe²⁺/Fe³⁺为载流子传递介质时可以实现水的完全分解(H₂/O₂体积比为2:1), 8 mmol·L^-1的FeCl₃作为初始载流子传递介质时, 产氢、产氧活性分别为66.8和31.8 μmol·h^-1, 氢氧体积比为2.1:1. 受光催化材料对载流子传递介质氧化还原速度的限制, 过高的载流子传递介质浓度并不能提高光催化活性.