Studies on graft copolymerization onto cellulose derivatives. XXVII. Photo-induced graft copolymerization onto nitrocellulose

Photo-induced graft copolymerization was investigated using nitrocellulose having a different nitrogen content, especially by a noncatalytic method. The effects of a sample nitrogen content, reaction temperature, and monomer, sample, solvent and photosensitizer concentrations on the degree of grafting, the grafting efficiency, and the apparent number of grafted chains were examined. Methyl methacrylate (MMA) and methyl acrylate (MA) easily polymerized, but acrylamide (AAm), vinyl acetate (VAc), and styrene (St) scarcely polymerized. The apparent activation energies were 4.1–11.5 kcal/mol, indicating the small value in the high nitrogen content sample. The degree of grafting and the apparent number of grafted chains increased with increasing monomer and sample concentrations. In every case, the grafting efficiency was at a high level, above 90%. The polymerization did not occur without the sample in the same condition. Furthermore, a part of nitro groups split off by the irradiation of light. With respect to these results, the mechanisms of the photo graft copolymerization was discussed.     

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.     

Graft copolymerization of 2-hydroxyethyl methacrylate and methyl methacrylate onto hide powder

Graft copolymerization of 2-hydroxyethyl methacrylate(HEMA) and mixtures of HEMA with methyl methacrylate (MMA) onto hide powder was attempted using ceric ammonium nitrate as initiator, with a view to optimize the conditions for graft copolymerization. Percent grafting and grafting efficiency were calculated for various variables such as monomer concentration, initator concentration and mole ratio of HEMA to MMA. R_p, R_g and R_h (rates of polymerization, grafting and homopolymerization respectively) were also evaluated. It was observed that R_p increased linearly with increasing concentration of MMA except at very low concentrations of the monomer. An explanation is given for the effect of variables on extent of grafting and grafting efficiency.     

Potassium diperiodatonickelate‐initiated graft copolymerization of methyl acrylate onto organophilic montmorillonite

Using potassium diperiodatonickelate (Ni (IV)) as an efficient initiator, the graft copolymerization of methyl acrylate (MA) onto organophilic montmorillonite (OMMT) was successfully performed in an alkaline medium. Three grafting parameters were systematically evaluated as functions of the temperature, the initiator concentration, reaction time, pH value, and the ratio of MA to OMMT substrate. The structure of the titled graft copolymers (OMMT‐g‐PMA) were confirmed by Fourier transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD), differential scanning calorimetry (DSC), and thermo‐gravimetric analysis (TGA). It was found that Ni (IV) was a highly efficient initiator for graft copolymerization of the MA onto OMMT, i.e., grafting efficiency is as high as 95% and grafting percentage can be facilely controlled within 700% in this study. In addition, the highest grafting efficiency and grafting percentage were obtained when temperature adopted was over 40°C and pH was about 10.3. A single‐electron‐transfer mechanism was proposed to illustrate the formation of radicals and the initiation reaction. Copyright © 2008 John Wiley & Sons, Ltd.     

Gamma radiation induced graft copolymerization of vinyl monomers onto poly(vinyl alcohol)

In an attempt to modify water-soluble synthetic polymers, graft Copolymerization of methylmethacrylate (MMA) and ethyl acrylate (EA) onto poly(vinyl alcohol), PVA, has been studied by using gamma irradiation from a Co⁶⁰ source as initiator. The graft copolymerization was carried out in an aqueous medium by the mutual method in air. The effect of total dose and concentration of vinyl monomers on percentage of grafting has been determined. Water plays a significant role in the enhancement of graft copolymerization and the optimum amount of water to afford maximum grafting has been evaluated. The effect of CH₃OH on aqueous grafting of MMA and EA by radiation method has been studied. The graft copolymer has been characterized by IR spectroscopic and thermogravimetric methods.     

Synthesis and Characterization of Bagasse Poly(methyl methacrylate) Graft Copolymer

Summary: Graft copolymerization of methyl methacrylate (MMA) was carried out on bagasse fibers in an aqueous medium using ceric ammonium nitrate (CAN) as initiator under a neutral atmosphere. In order to obtain the optimum condition for graft copolymerization, the effects of initiator concentration, temperature, time of reaction, and monomer concentration were studied. The maximum grafting percent was found to be 122%. The bagasse grafted poly(methyl methacrylate) was characterized by FTIR and its thermal behavior was characterized by TGA.     

Characterization of methyl methacrylate grafting onto preirradiated biodegradable lignocellulose fiber by gamma-radiation

Gamma-radiation-induced graft copolymerization of methyl methacrylate onto natural lignocellulose (jute) fiber was carried out by the preirradiation method in an aqueous medium by using octylphenoxy-polyethoxyethanol as an emulsifier. The different factors that influenced the graft copolymer reaction process were investigated. In the case of radiation-dose-dependent grafting, samples irradiated in the presence of air produced up to 73% graft weight compared to 53% obtained in the case of irradiation in a nitrogen environment. By assuming Arrhenius reaction kinetics, the activation energy (E(a)) of the grafting reaction process was evaluated for different reaction temperatures. Moreover, the graft copolymer reaction was controlled by incorporating a homopolymer-inhibiting agent and three different chain-transfer agents in the reaction medium. The mechanical and thermal properties of jute fiber 'as received' and jute-graft-poly(methyl methacrylate) were also investigated. The results showed that the percentage of grafting with jute fiber has a significant effect on the properties. The kinetic parameters were evaluated from TGA thermograms by using Broido's method in the temperature range 240-350 degrees C. Scanning electron micrographs show that the structural changes on the surface of jute fibers were induced by graft copolymerization of methyl methacrylate monomer. Fiber-fiber surface friction was measured in terms of the average maximum load and the kinetic friction. SEM of jute-graft-poly(methyl methacrylate).     

Grafting onto Wool. XV. Graft Copolymerization of MA and MM A by Use of Mn(acac)3 as Initiator

Graft copolymerization of acceptor monomers MA and MMA onto Himachali wool fiber in an aqueous medium was studied by using Mn(acac)s as initiator. Nitric acid was found to catalyze the graft copolymerization. Percentage of grafting and percent efficiency have been determined as functions of the concentration of chelate, nitric acid, monomer, time, and temperature, Under optimum conditions, MMA produced a maximum grafting of 82.5% while MA afforded maximum grafting to the extent of 27.5%. Relative reactivities of MA and MMA toward grafting have been compared with those of EA, BA, and VAc reported earlier from this laboratory. Different vinyl monomers were found to follow the following reactivity order toward grafting onto wool fiber in the presence of Mn(acac)₃: MMA > EA > BA > MA > VAc. An attempt has been made to explain the observed reactivity pattern shown by different vinyl monomers in graft copolymerization reactions.     

Surface modification of coir fibers I: studies on graft copolymerization of methyl methacrylate on to chemically modified coir fibers

Graft copolymerization of methyl methacrylate (MMA) onto chemically modified coir fiber was studied using a CuSO₄–KIO₄ combination as initiator in an aqueous medium in the temperature range of 50–70 °C. Concentrations or [IO₄−] = 0.005 mol/l and [Cu2+] = 0.002 mol/l produce optimum grafting. The effects of time, temperature, amount of coir fiber, some inorganic salts and organic solvents on graft yield have also been investigated. On the basis of experimental findings, a reaction mechanism has been proposed. Evidence of grafting was studied from fourier transform infrared spectroscopy and scanning electron microscopy of chemically modified coir and MMA‐grafted coir. Tensile properties such as maximum stress at break, extension at break and Young's modulus of untreated, defatted, chemically treated and grafted coir fibers were evaluated and compared. Grafted coir fiber showed an increase in tensile properties such as maximum stress at break, extension at break and Young's modulus. Copyright © 1999 John Wiley & Sons, Ltd.     

Grafting onto Wool. IX. Graft Copolymerization of Vinyl Monomers by Use of Vanadium Oxyacetylacetonate as Initiator

Methyl methacrylate (MMA), acrylic acid (AAc), and vinyl acetate (VAc) were graft copolymerized onto Himachali wool in an aqueous medium by using vanadium oxyacetyl acetonate as initiator. Graft copolymerization was studied at 45, 55, 65, and 75°C for various reaction periods. The percentage of grafting was determined as functions of concentration of monomers, concentration of initiator, time, and temperature. The maximum percentage of grafting with each monomer occurred at 55°. Several grafting experiments were carried out in the presence of various additives which include HNO3, DMSO, and pyridine. Nitric acid was found to promote grafting of MMA. All these additives had adverse effects on grafting of VAc and AAc. MMA, VAc, and AAc were found to differ in reactivity toward grafting and followed the order MMA > AAc > VAc.     

尼龙66与甲基丙烯酸甲酯接枝共聚合的研究——DMA/硫酸铜引发体系

烯类单体与聚酰胺(尼龙)纤维接枝共聚合已有报道.Varma等人研究了Ce4+引发丙烯腈、丙烯酰胺分别与尼龙纤维的接枝共聚反应。Lenka发表了用P2O48-引发甲基丙烯酸甲酯(MMA)与尼龙6纤维接枝共聚合的研究结果.Nayak等人报道了用乙酰丙酮锰为引发剂使MMA与尼龙6接枝共聚合.本文以二甲基苯胺(DMA)/硫酸铜为引发体系,用MMA接枝尼龙66纤维丝,研究了Cu2+浓度等因素对该接枝共聚反应的影响.     

Mechanism of graft copolymerization of styrene onto deproteinized natural rubber

High conversion and high grafting efficiency attained by graft copolymerization of styrene onto deproteinized natural rubber (DPNR) was investigated with respect to the molecular weight of grafted polystyrene. The graft copolymerization was performed with tert-butyl hydroperoxide/tetraethylenepentamine as an initiator after deproteinization of natural rubber with urea. Grafted polystyrene was isolated from the resulting graft copolymer by ozonolysis reaction. After the ozonolysis of the graft copolymer of DPNR and polystyrene (DPNR-g-PS), the molecular weight of grafted polystyrene was determined by size exclusion chromatography. Effects of initiator and monomer concentrations were investigated with respect to the molecular weight of the grafted polystyrene, which was found to depend on not only the number of active site generated on the rubber particle but also the feed of styrene. Deactivation and chain transfer of the active sites were attributed to effective amount of styrene used for the graft copolymerization.     

Graft Copolymerization of Methyl Methacrylate onto Chitosan Initiated by Potassium Ditelluratocuprate(III)

A novel redox system, potassium ditelluratocuprate(III) (DTC)–chitosan, was employed to initiate the graft copolymerization of methyl methacrylate (MMA) onto chitosan in alkali medium. The effects of reaction variables, such as the initiator concentration, ratio of monomer to chitosan, the pH value, as well as reaction temperature and time were investigated, and the grafting conditions were optimized. Graft copolymers with both high grafting efficiency (>90%) and percentage of grafting were obtained, and the rate of polymerization is higher, which indicated that the DTC–chitosan redox system is an efficient initiator for this graft copolymerization. The structures and the thermal property of chitosan and chitosan–g–PMMA were characterized by infrared spectroscopy (IR), X‐ray diffraction and thermogravimetric analysis (TGA). A mechanism is proposed to explain the generation of radicals and the initiation. The graft copolymer was used as the compatibilizer in blends of terpolyamide and chitosan. The scanning electron microscope (SEM) photographs indicated that the graft copolymer improved the compatibility of the blend.     

Graft copolymerization of methacrylic acid onto carboxymethyl chitosan

Carboxymethyl chitosan (CMCTS) was prepared and characterized by FTIR, ¹H NMR, and elemental analysis. The graft copolymerization of methacrylic acid (MAA) onto CMCTS using ammonium persulfate (APS) as an initiator was carried out in an aqueous solution. Evidence of grafting was obtained by comparison of FTIR spectra of CMCTS and the grafted copolymer as well as solubility characteristics of the products. The effects of APS, MAA, reaction temperature and time on graft copolymerization were studied by determining the grafting parameters such as grafting percentage and grafting efficiency. With keeping other conditions constant, the optimum conditions were shown as following: [APS]=8 mmol/l, [MAA]=2.4 mol/l, reaction temperature=60-70 °C, reaction time=120 min.     

Synthesis and characterization of poly(methyl methacrylate)/casein nanoparticles with a well‐defined core‐shell structure

Well‐defined, core‐shell poly(methyl methacrylate) (PMMA)/casein nanoparticles, ranging from 80 to 130 nm in diameter, were prepared via a direct graft copolymerization of methyl methacrylate (MMA) from casein. The polymerization was induced by a small amount of alkyl hydroperoxide (ROOH) in water at 80 °C. Free radicals on the amino groups of casein and alkoxy radicals were generated concurrently, which initiated the graft copolymerization and homopolymerization of MMA, respectively. The presence of casein micelles promoted the emulsion polymerization of the monomer and provided particle stability. The conversion and grafting efficiency of the monomer strongly depended on the type of radical initiator, ROOH concentration, casein to MMA ratio, and reaction temperature. The graft copolymers and homopolymer of PMMA were isolated and characterized with Fourier transform infrared spectroscopy and differential scanning calorimetry. The molecular weight determination of both the grafted and homopolymer of PMMA suggested that the graft copolymerization and homopolymerization of MMA proceeded at a similar rate. The transmission electron microscopic image of the nanoparticles clearly showed a well‐defined core‐shell morphology, where PMMA cores were coated with casein shells. The casein shells were further confirmed with a zeta‐potential measurement. Finally, this synthetic method allowed us to prepare PMMA/casein nanoparticles with a solid content of up to 31%. Thus, our new process is commercially viable. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3346–3353, 2003     

Grafting Vinyl Monomers onto Wool Fibers: Graft Copolymerization of Methyl Methacrylate onto Wool Using Ferric Acetylacetonate Complex

The graft copolymerization of methyl methacrylate (MMA) onto native and reduced Indian Chokla wool fibers was studied in aqueous solution using an acetylacetonate complex of Fe(III). Perchloric acid was found to catalyze the reaction. The rate of grafting was investigated by varying the concentration of the monomer and the complex, the acidity of the medium, and the solvent composition of the reaction medium. The graft yield increases with increasing concentration of the initiator and with increasing temperature. An increase of monomer concentration up to 0.5634 mol/L and of the HClO4 concentration up to 0.01 mol/L increases the graft yield. Reduced and oxidized wools were found to be better substrates than untreated, esterified, cross-linked, and trinitrophenylated wools. Among the various monomers studied, MMA was found to be the most active. A suitable kinetic scheme is proposed. From the activation energy data, average molecular weight, and spectral studies, the reactivity of -SH groups, and the extent of chain transfer is ascertained.     

Grafting Vinyl Monomers onto Silk Fibers: Graft Copolymerization of Vinyl Monomers onto Silk Using the Vanadyl Acetylacetonate Complex

Abstract

The graft copolymerization of methyl methacrylate (MMA) onto mulberry silk fibers was studied in aqueous solution using the acetylacetonate oxovanadium (IV) complex. The rate of grafting was investigated by varying the concentration of the monomer and the complex, the acidity of the medium, the solvent composition of the reaction medium, the surfactants, and the inhibitors. The graft yield increases with increasing concentration of the initiator up to 8.75 × 10^?5 mol/L, of the monomer up to 0.5634 mol/L, and thereafter it decreases. Among the various vinyl monomers studied, MMA was found to be most suitable for grafting. Grafting increases with increasing concentration of HCIO₄ and with increasing temperature. Inhibitors like picryl chloride and hydroquinone significantly decrease the extent of grafting. Alcoholic solvents at a solvents/water ration of 10:90 seem to constitute the most favorable medium for grafting. A suitable reaction scheme has been proposed, and the activation energy calculated from the Arrhenius plots.     

Effects of solvent in photo-induced graft copolymerization of vinyl monomers on cellulose

The effects of swelling of the sample and polymerization solvents were studied for photo-induced graft copolymerization of vinyl monomers on cellulose. The graft copolymerization of methyl methacrylate (MMA) was activated by swelling of the sample or organic solvent-water solutions within a certain range of their concentrations. Though each organic solvent gave a maximum in per cent grafting and the number of grafts at about 25 vol-% concentration, the initiation reaction scarcely took place at 100% concentration; thus, the solvent itself is considered to have a negative effect. The solvents used in the experiments were all hydrophilic, such as methanol, acetone, and dioxane. The average molecular weight of the grafted PMMA differed in each solvent, indicating a different characteristic effect of solvent on the growing grafted polymer radicals. The presence of ferric ion as a sensitizer stimulated further the contributions of the sample swelling and the organic solvents to the copolymerization reaction. A similar effect was observed for styrene as for MMA, but not for acrylic acid and methacrylic acid.     

Ascorbic Acid/H2O2-initiated Graft Copolymerization of Methyl Methacrylate onto Abelmoschus Esculentus Fiber: A Kinetic Approach

Graft copolymerization of methyl methacrylate onto lignocellulosic Abelmoschus esculentus fibers was successfully carried out in aqueous medium using ascorbic acid and hydrogen peroxide as redox initiator. Maximum percentage of grafting was achieved when the concentrations of ascorbic acid, hydrogen peroxide, and monomer were 3.85 × 10^?2, 2.41 × 10^?1, and 1.87 × 10^?1 mol/L respectively at a temperature of 45°C for a reaction time of 90 min. The kinetics of graft copolymerization was also studied, and it was found that the rate expression for graft copolymerization is (R_g) = K [Asc]^0.68[H₂O₂]^0.49[MMA]^1.17. The activation energy for graft copolymerization of MMA onto Abelmoschus fiber was found to be 12.48 KJ/mol. The graft copolymers thus formed were characterized by FT-IR spectroscopy, scanning electron microscopy and thermogravimetric analysis.     

Graft copolymerization of 4-vinylpyridine onto cellulose using Co (III) acetylacetonate comlex in aqueous medium

The graft copolymerization of 4-vinylpyridine (4-VP) onto cellulose has been carried out in heterogeneous conditions with cobaltacetylacetonate complex (Co (acac)₃) under nitrogen atmosphere at 35±0.1°C in aqueous media. The grafting parameters such as graft yield, grafting efficiency, total conversion, frequency of grafting and rate of grafting have been evaluated as a function of concentration of 4-vinylpyridine, cobaltacetylacetonate and reaction temperature of graft copolymerization. Variation in concentration of monomer and initiator leads to a consistent increase in grafting parameters and then show a decreasing trend. The efficient grafting of monomer in presence of cobaltacetylacetonate complex is due to the coordination of the -electrons of the 4-vinylpyridine with the metal chelate which facilitate the homolytic decomposition of metal-oxygen bond to form radicals at relatively low temperature. The rate of graft copolymerization is directly proportional to the concentration of monomer and the square root of the concentration of the cobaltacetylacetonate complex. The activation energy (Ea) for graft copolymeriztion has been calculated using a Arrhenius plot and is 31.0kJ mol^–1 within the temperature range of 20–40°C. The grafting of 4-vinylpyridine has also been studied in presence of various additives and their effects have been suitably explained. On the basis of the experimental observations, reaction steps are proposed and rate expression has been derived.