Influence of glycine on the kinetics of the graft copolymerization of acrylonitrile onto jute fibers initiated by ceric ion

A study of the influence of glycine on the graft copolymerization of acrylonitrile (AN) onto jute fiber using ceric ion has been made. The effect of concentrations of monomer, Ce (IV), and glycine on graft yield have been studied. In addition, the effect of time, temperature, acid, and the amount of jute fiber on graft yield has been investigated. On the basis of experimental findings, a qualitative reaction mechanism has been proposed and the optimum condition for effective grafting has been suggested.     

ESR study of reactions of cellulose initiated by the ceric ion method

The ESR spectra of microcrystalline cellulose and purified cotton cellulose reacted with ceric ammonium nitrate in nitric acid were determined. The effects of the concentration of ceric ion, atmosphere, temperature, and graft copolymerization with acrylonitrile on the rates of formation and decay of radicals in the cellulose molecule were determined under both static and dynamic conditions. Under static conditions, after the desired conditions of reaction, the samples were frozen at –100 or –160°C., and then the concentration of free radicals was determined. Under dynamic conditions ceric ion solution was continuously flowed through the celluloses while these determinations were being made at 25°C. In the presence of oxygen the rate of decay of free radicals was decreased. On initiation of copolymerization reactions with acrylonitrile, there was an increase in radical concentration, then a decrease. Apparently, during graft copolymerization the radical site initially on the cellulose molecule was retained on the end of the growing polymer chain. Then additional ceric ion coordinated with the hydroxyl groups of the cellulose, leading to the formation of additional radical sites. An Arrhenius interpretation of the effect of temperature on the formation of these additional radical sites gave apparent activation energies for radical formation on cotton cellulose as 34 kcal./mole and on microcrystalline cellulose as 29 kcal./mole.     

Grafting of acrylonitrile onto different cellulose forms by the xanthate method

Wood pulp and regenerated cellulose (viscose fibres) were grafted by the xanthate method. In some cases, the regenerated cellulose was more accessible towards grafting than wood pulp. Grafting of incompletely regenerated viscose fibres which were obtained by changing the spinning conditions in order to spare the step of partial xanthation caused more orientation of the filaments. The mechanical properties of these filaments were in general poor.     

Grafting of methyl methacrylate onto cellulose nitrate initiated by benzoyl peroxide

It has been observed that grafting of vinyl monomers onto cellulose nitrate in solution takes place using benzoyl peroxode. The graft copolymer was isolated from the unreacted backbone and homopolymer by selective solvent extraction. The effect of variables, such as the initiator concentration, the monomer concentration and the reaction time on the percent grafting and the grafting efficiency, were discussed. A probable mechanism for grafting of vinyl monomers to cellulose nitrate in solution has been proposed.     

Influence of dimethyl sulfoxide on the kinetics of the graft copolymerization of acrylonitrile onto the jute fibers initiated by ceric ion

A study of the influence of dimethyl sulfoxide (DMSO) on the graft copolymerization of acrylonitrile (AN) onto jute fiber using ceric ion has been made. The effect of concentrations of monomer, Ce(IV) and DMSO on graft yield have been studied. Besides, the effect of time, temperature, acid, and the amount of jute fiber on graft yield has been investigated. On the basis of experimental findings, a reaction mechanism has been proposed and optimum condition for effective grafting has been suggested.     

Grafting of acrylonitrile onto styrene-maleic acid copolymer by tetravalent cerium ion

The graft copolymerization of acrylonitrile (AN) onto a styrene-maleic acid copolymer (SY-MAc) with ceric ammonium nitrate (CAN) as a redox initiator in an aqueous medium has been studied. The effects of various reaction parameters, including reaction time and temperature, concentrations of initiator, nitric acid, and monomer, on the grafting yields and the rates of polymerization (R_p), graft copolymerization (R_g), and homopolymerization (R_h) were studied systematically. The results are discussed. The kinetic scheme of free-radical graft copolymerization has been proposed and the equations relating the values of R_p, R_g, and R_h are also suggested. The experimental results are found to be in good agreement with the proposed kinetic scheme. The activation energies of graft copolymerization and total polymerization are calculated. © 1995 John Wiley & Sons, Inc.     

Oxidation of cellulose by ceric ion

Dissolving pulp was oxidized by ceric ammonium sulfate in sulfuric acid medium under oxygen-free argon. Initial rapid oxidation was followed by first-order consumption of ceric ion. The rate of cellulose oxidation (?R_Ce) which was taken at the beginning of the first order consumption period, levelled off with an increase in the concentration of ceric ion. It was found that the ?R_Ce was dependent on the concentration of cellulose in the second power. The rate of ceric ion consumption was a function of the available surface area of cellulose.     

Grafting of poly(triethylene glycol dimethacrylate) onto chitosan by ceric ion initiation

Grafting of poly(triethylene glycol dimethacrylate) (poly(TriEGDMA)), onto chitosan by ceric ion initiation has been investigated. The grafting conditions were optimized by studying the effect of monomer and initiator concentrations as well as time and temperature. Products with lower grafting yields (90–261%) were water and acid soluble. Those with higher grafting yields (350–868%) were insoluble, indicating a cross linked structure. Chitosan-graft- poly(TriEGDMA) products had a lower thermal stability than chitosan as revealed by DSC analysis. C-13 NMR and FTIR analyses suggested a grafting mechanism that proceeds via oxidation and chain scission of chitosan. The products are degraded by the enzymes lysozyme, lipase and α-amylase–protease.     

Grafting of acrylonitrile and methyl methacrylate from their binary mixtures on cellulose using ceric ions

Ceric ion‐initiated grafting on cellulose from a binary mixture of acrylonitrile and methyl methacrylate was carried out in heterogeneous and acidic conditions at 30 ± 0.1°C in a nitrogen atmosphere. To avoid the complexation of water molecules with Ce(IV) ions, the concentration of the nitric acid was taken to be more than the concentration of ceric ions. The effect of the feed concentration, reaction time, and ceric ions concentration on grafting were investigated at a fixed composition. To investigate the effect of monomer–monomer interactions on grafting, the graft copolymerization was also studied, using different feed compositions (f_AN) ranging from 0.25 to 0.80. In this range of feed composition, the synergistic effect of methyl methacrylate molecules has shown an important effect on acrylonitrile monomer and facilitate the incorporation of the acrylonitrile monomer into the grafted chains. The reactivity ratios of acrylonitrile and methyl methacrylate were calculated using the Mayo and Lewis method and were found to be 0.74 and 1.03, respectively. The average sequence lengths of the monomers (m̄M) were found to be dependent on the feed compositions and found to be arranged in alternate fashion in the grafted chains. The probability of the addition of a monomer (P_1,1) to the growing radicals on cellulose ended with its own type of monomer was found to be dependent on the feed composition. The composition of the grafted copolymers, homocopolymers, was determined by IR and elemental analysis for nitrogen. None of the grafted chain on cellulose was found to be made of a single type of monomer. The ceric ion consumption during grafting was found to be independent of the molarity of the feed but shown an appreciable change in the initial few hours of grafting. The variation in the values of the grafting parameters as a function of the reaction conditions is suitably explained. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 767–778, 2001     

Preparation and characterization of hydrogels obtained by grafting of acrylonitrile onto cassava starch by ceric ion initiation

Graft starch-polyacrylonitrile copolymers have been obtained from cassava starch (yucca starch or tapioca), which was pre-heated at 65 and 95°C for different lengths of time. The copolymerization was carried out by using ceric ion as initiator at different concentrations (2.0 to 8.0 mmol/L) and also varying both the length of time of copolymerization and the ratio of monomer to starch. The composition, or grafting parameters, of all the obtained copolymers was determined by weight difference after they were extracted with dimethylformamide and hydrolyzed with an acidic solution. Samples of these copolymers were also hydrolyzed with an aqueous solution of potasium bydroxide to produce the corresponding hydrogels, and its absorbency in water was determined. © 1993 John Wiley & Sons, Inc.     

Grafting of methyl methacrylate onto collagen initiated by tributylborane

The graft copolymerization of methyl methacrylate onto collagen initiated by tributylborane was investigated in aqueous medium. The total conversion, percentage of grafting and efficiency of grafting increased with increasing collagen content. The optimum conditions on the percentage of grafting and efficiency of grafting were determined by varying initiator concentration, monomer concentration, and polymerization temperature. The grafting onto denaturated collagen was also studied. It has been suggested that the grafting onto collagen proceeds by a radical mechanism via a complex of TBB and hydrated collagen.     

Graft copolymerization of acrylonitrile onto hemicellulose using ceric ammonium nitrate

The ability of ceric ammonium nitrate to induce graft copolymerization of acrylonitrile onto hemicellulose was investigated. The graft yield depends on monomer and initiator concentrations as well as reaction time and temperature. Chemical analysis of the reaction product of hemicellulose and acrylonitrile in the presence of ceric ammonium nitrate revealed that the ceric ammonium nitrate acted as initiator for polymerization of acrylonitrile and as oxidizing agent for hemicellulose. Proof for grafting of hemicellulose was provided through IR analysis.     

Grafting biodegradable polyesters onto cellulose

To increase the compatibility between cellulose fibers and polyester matrix an original method for grafting hydrophobic oligoesters onto cellulose was proposed. Two kinds of cellulose substrates were employed as cellulose films and microcrystalline cellulose powder. Different oligoesters containing reactive end groups based on poly(DL ‐lactic acid) PDL‐LA, poly(ε‐caprolactone) PCL and poly(3‐hydroxyalkanoate)s PHA were first prepared and characterized by size exclusion chromatography (SEC), nuclear magnetic resonance (NMR), and differential scanning calorimetry (DSC). The carboxylic end groups of the polyesters were activated using thionyl chloride (SOCl₂) to increase the esterification reaction with the hydroxyl groups of the cellulose. The esterification was realized in a heterogenous medium without any catalyst by deposition of chloride oligoesters in solution (2–100 g L⁻¹) onto cellulose film at different temperatures (25–105°C) during 1–12 h. The successful grafting on the various substrates was confirmed on the basis of FTIR spectroscopy, contact angle measurement, X‐ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA). In particular, it is shown that a small quantity of grafted oligoesters led to a significant increase of the hydrophobic character of the cellulose with a contact angle near 130°. The increase of hydrophobicity of cellulose is independent of the nature and length of grafting oligoesters. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Graft copolymerization of acrylonitrile onto allylated caesarweed fibres by ceric ion in the presence of 2‐mercaptoethanol

Polyacrylonitrile was grafted onto caesarweed fibers and on the allyldervative in aqueous media by ceric ion‐2‐mercaptoethanol redox pair. The allylfibre was obtained by treatment of caesarweed fibers with sodium hydroxide followed by allylchloride in diisoproylether to yield an average degree of substitution of 3.24 allyl moieties per anhydroglucose unit (AGU). The graft yield dependence on 2‐mercaptoethanol concentration, in the range, 10.7–64.0 × 10^?4M was characterized by a minimum followed by an enhanced yield. This suggested the existence of two initiating species, a thioglycol radical and mercaptoethoxyl radical. A fivefold increase in the concentration of 2‐mercaptoethanol was accompanied by reduction in the frequency of graft, F_g from 75.6–0.79 Ng/10⁴ AGU and a concomitant increase, by two orders of magnitude, in the average molecular weight of grafted polymer M_v, with values of up to 11.78 × 10⁵. Infrared spectroscopy of allylfibre‐g‐polyacrylonitrile copolymer showed evidence of radical coupling reaction involving thioglycol radical species and allylic macroradicals of the allylfibre. The unmodified fiber was more reactive than the allylfibre by as much as a factor of 2, and was ascribed to resonance stabilization of allylic macro radicals derived from the latter. For the allyl fiber, a 150% increase in monomer concentration resulted in nominal increase in graft yield, not higher than 7%. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Grafting vinyl monomers onto cellulose. I. Graft copolymerization of methyl methacrylate onto cellulose using quinquevalent vanadium ion

Graft copolymerization of methyl methacrylate on cellulosic materials with the use of quinquevalent vanadium as an initiator was studied. Increase of V⁵⁺ion concentration up to 0.0025 mole/liter increases graft yield, and with further increase of the initiator the graft yield decreases. The graft yield increases with increase of monomer concentration. The increase of acid concentration is accompanied by decrease of graft yield. A measurable increase in graft yield was observed with increase in temperature from 65 to 75°C. The graft yield is medium and substrate dependent. A suitable kinetic scheme has been pictured and a rate equation has been derived.     

Grafting of vinyl monomers onto wood fibers initiated by peroxidation

Summary The oxidation of chemithermomechanical (aspen) pulp with ruthenium tetroxide followed by peroxidation with hydrogen peroxide was performed to study the graft copolymerization of methacrylic acid, epoxypropyl acrylate and epoxypropyl methacrylate. For epoxy monomers, lower pH (i.e. < 5) is more favorable due to the participation of the epoxy group in the grafting reaction in acidic medium. Moreover, the grafting of epoxy monomers appeared more efficient than methacrylic acid.     

Grafting of methyl methacrylate onto silk fibers initiated by tri-n-butylborane

Structural characteristics of the methyl methacrylate (MMA)-grafted silk fibers using tri-n-butylborane as an initiator were analyzed by infrared spectroscopy and differential scanning calorimetry (DSC), and their refractive index and tensile properties were measured. Graft polymerization was promoted by FeCl₃ pretreatment of the silk. The graft yield reached a maximum by the immersion in 4% FeCl₃ solution for 1 min at 25°C. The infrared spectrum of poly(MMA)-grafted silk fibers showed overlapped absorption bands of silk fibroin with the β structure and of the grafted MMA polymer. A grafted silk fiber with graft yield of more than 140% exhibited two endothermic peaks at 321°C and 396°C on the DSC curve, attributed to the thermal decomposition of silk fibroin and grafted poly(MMA) chain, respectively. Refractive index measurements suggested that the molecular orientation and the crystallinity of the silk fiber decreased with increasing graft yield. Electron photomicrographs showed that silk was coated by grafted PMMA. The tensile strength of the grafted silk decreased rapidly by the grafting even at a lower level.     

Grafting of a styrene–acrylonitrile binary monomer mixture onto cellulose extracted from pine needles

In an attempt to develop new reactive membrane materials, we graft‐copolymerized styrene (Sty) and acrylonitrile (AN) onto cellulose extracted from pine needles by a chemical initiation method. The optimum grafting reaction conditions for Sty onto cellulose were earlier evaluated as [Sty] = 656.25 mmol/L and [potassium persulfate–ferrous ammonium sulfate] = 146.3:12.75mmol/L in 20 mL of H₂O with a reaction time of 3 h and a reaction temperature of 60°C for 1 g of cellulose. Under these conditions, Sty was graft‐copolymerized with AN at five different concentrations of the latter. Grafting parameters and different rates of concentration were evaluated. The effects of additives such as ZnCl₂, LiNO₃, and Cu(NO)₃ were studied at the best comonomer concentration of Sty–AN. In the presence of ZnCl₂, Sty–AN graft‐copolymerized in an alternate way, thus, making it evident that ZnCl₂ coordinated to form a “complexomer,” or complex of monomers [Sty^?AN⁺…ZnCl₂], of two monomers. Evidence of the structural characteristics of grafted chains were provided by characterization with elemental analysis, thermal analysis, and Fourier transform infrared spectroscopy. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2000–2007, 2002