Modification of Tefzel film through graft copolymerization

The graft copolymerization of styrene (st) and methacrylonitrile (MAN) onto Tefzel film in aqueous media by the preirradiation method has been studied. In order to follow the effect of preswelling of the backbone polymer, grafting was attempted onto preirradiated Tefzel film and monomer preswollen, preirradiated Tefzel film. Optimum conditions pertaining to maximum percentage of grafting of st and MAN have been evaluated. Grafting onto preswollen, preirradiated Tefzel film displayed better results. The effect of different alcohols of increasing chain length on the percentage of grafting of st and MAN was also studied. Graft copolymerization of st showed an increase, while grafting with MAN exhibited a decrease, in the percentage of grafting in the presence of alcohols as compared to that obtained in the aqueous medium. Characterization of the graft copolymers was made by IR and thermogravimetric studies. Tefzel‐graft‐polystyrene showed improved thermal stability while the MAN grafted onto preswollen, preirradiated Tefzel film produced graft copolymer with poor thermal stability. Copyright © 2004 Society of Chemical Industry     

Behavior of cellulose grafted with poly(methyl methacrylate) and polyacrylonitrile toward some direct and reactive dyes

Viscose rayon fibers modified with polyacrylonitrile (PAN) and poly(methyl methacrylate) (PMMA) were dyed with some direct and reactive dyes. Exhaustion rate of the dye onto fibers was governed by the amount and nature of the polymer grafted. In general, the dye affinity for cellulose and dye exhaustion onto fibers decreased as the graft yield increased. Dye affinity for the PAN–cellulose graft copolymers was greater than that found with PMMA–cellulose graft copolymers. Except in a few cases, the tendency of cellulose graft copolymers of ca. 13% graft to accept direct dyes was more than that of the untreated cellulose, whereas the affinity of reactive dyes for cellulose graft copolymers of up to ca. 43% polymer was more than that of untreated cellulose. The dye fixation, based on the weight of cellulose component, increased as the graft yield increased. The dyeability of cellulose oxidized with ceric ammonium nitrate was also examined. Oxidation of cellulose prior to dyeing reduced the affinity of the dye for cellulose.     

Structure and properties of cellulose graft copolymers. I. Radiation-induced rayon–styrene graft copolymer

Rayon–styrene graft copolymers were prepared by the direct radiation method, with the use of the preswelling technique, by irradiation with γ-rays from ⁶⁰Co. The grafting was carried out in bulk styrene and in styrene–solvent mixtures, such as styrene–methanol and styrene–acetone, to study their effect on the graft copolymerization reaction and the structure of the resulting graft copolymer. The effects of carbon tetrachloride, a chain-transfer agent, was also investigated. Three different types of rayon yarn were used; Fortisan, a modifier-type high wet-modulus rayon, and a high-tenacity tire yarn, in order to study the effect of rayon microstructure on the grafting reaction. The molecular structure of the rayon–styrene graft copolymers was studied by hydrolyzing away the cellulose backbone and measuring the molecular weights of the grafted polystyrene branches. For grafting in bulk styrene, the molecular weights of the grafted polystyrene ranged from 400,000 to 1,000,000, while those of the polystyrene homopolymer formed in the outside solution were of the order of 30,000–50,000. The molecular weights of the grafted polystyrene branches tended to increase with per cent grafting in the graft copolymer. For grafting in styrene–methanol and styrene–acetone mixtures, the molecular weights of the polystyrene branches decreased with increasing solvent content. The addition of carbon tetrachloride to bulk styrene resulted in a sharp decrease in the molecular weights of the grafted branches. The grafting frequency or number of polystyrene branches per cellulose chain was calculated from the per cent grafting and the molecular weights of the polystyrene branches. The morphology of the rayon–styrene graft copolymers and some of their physical properties are discussed.     

Gamma radiation-induced graft copolymerization of divinylbenzene onto cellulose fabric

The extent of DVB grafting onto cellulose fabric increases with total gamma radiation dose up to 10–15 kGy while it decreases with the radiation dose rate. A quantitative analysis of DVB grafting has been attempted by means of IR spectroscopy using the baseline method. Characteristic bands were selected in the spectra of copolymers, namely, the cellulose band at 1160 cm^?1 and DVB band at 798 cm^?1. The former band decreased and the latter increased with the degree of copolymerization, and the values were in accordance with the calibration straight line. An attempt to graft DVB onto cotton fabric previously grafted with styrene showed greater extent of copolymerization than with pure fabric.     

Grafting of dichlorodimethylsilane onto cellulose acetate as a model system in homogeneous media

Homogeneous graft copolymerization of dichlorodimethylsilane (DCDMS) onto cellulose acetate (CA) was carried out in acetone. The weight conversion, grafting percentage and grafting efficiency were determined as functions of the polymerization temperature and the concentrations of monomer and cellulose acetate. The IR and NMR data of the graft copolymers showed peaks characteristic of grafted chains. The order of the solvents used for increasing the grafting yield values was found as follows: cyclohexanone > ethyl acetate > dioxane, which is in accordance with their dielectric constants. Cellulose acetate previously oxidized by treatment with a mixture of oxalic acid and potassium dichromate when grafted with DCDMS gave low grafting yield values. The rate of copolymerization grafting of DCDMS onto CA was determined (R_p = 1.1 %min⁻¹). The activation energy of the reaction between DCDMS and CA was calculated (1.32 kJ mol⁻¹, 0.32 kcal mol⁻¹). The mechanism of graft copolymerization of DCDMS onto CA is discussed.     

Radiation-initiated graft copolymerization of binary monomer mixtures containing acrylonitrile with cotton cellulose

By the use of the cobalt 60 postirradiation grafting technique, purified cotton cellulose fibers were graft-copolymerized with binary mixtures of acrylonitrile and other monomers, including styrene, 1,3-butylene dimethacrylate, vinylpyrrolidone, vinylidene chloride, and methyl, butyl, lauryl, glycidyl, and allyl methacrylates. The irradiated cotton fibers were immersed in solutions of the monomers at 25°C to initiate graft copolymerization. Solvents were water, methanol, dimethyl sulfoxide, and methyl ethyl ketone, alone or in several combinations. The extent of graft copolymerization and the composition of the grafted copolymer depended on the composition of the binary mixtures of monomers and on the solvent or mixtures of solvents used. For example, addition of styrene, 1,3-butylene dimethacrylate, or vinylpyrrolidone to acrylonitrile increased the extent of graft copolymerization to a maximum value; addition of vinylidene chloride or allyl methacrylate to acrylonitrile did not greatly affect the extent of graft copolymerization; and addition of methyl or glycidyl methacrylate to acrylonitrile increased the extent of graft copolymerization without passing through a maximum value. The proportion of acrylonitrile in the grafted copolymer was generally less than that in the binary mixtures. As the reaction time was increased, the extent of graft copolymerization increased to a maximum value; however, the composition of the grafted copolymer did not change significantly. Generally, the addition of water to the solutions increased the extent of graft copolymerization. The mechanisms of these graft copolymerization reactions are discussed.     

Synthesis and characterization of N‐vinyl pyrrolidone and cellulosics based functional graft copolymers for use as metal ions and iodine sorbents

To develop cost effective and eco friendly polymeric materials for enrichment and separation technologies, 1‐vinyl‐2‐pyrrolidone (N‐VP) was graft copolymerized onto cellulose, extracted from pine needles. Optimum conditions have been evaluated for the grafting of N‐VP onto cellulose and at these conditions it was also grafted onto cellulose phosphate, hydroxypropyl cellulose, cyanoethyl cellulose, and deoxyhydrazino cellulose. At the optimum grafting conditions for N‐VP, it was also cografted with maleic anhydride. Kinetics of radiochemical graft copolymerization has been studied and evaluation of the polymerization and grafting parameters as percent grafting, percent grafting efficiency, rate of polymerization, homopolymerization, and graft copolymerization have been evaluated. Graft copolymers have been characterized by elemental analysis, FTIR, and swelling studies. An attempt has been made to study sorption of some metal ions such as Fe²⁺ and Cu²⁺ and iodine on select graft copolymers to investigate selectivity in metal ion sorption and iodine sorption as a function of structural aspects of the functionalized graft copolymers to find their end uses in separation and enrichment technologies. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 373–382, 2005     

电子束预辐照纤维素接枝丙烯酸的研究

研究了高能电子束辐照纤维素棉纱接枝丙烯酸的主要影响因素。讨论了接枝反应机理,认为大分子自由基是电子束预辐照纤维素接枝丙烯酸的主要活性中心。对棉纱接枝物的应用作了探索性的研究。     

Polymer structure formed in radiation-induced graft polymerization

Methacrylic acid (MAA) and methyl methacrylate (MMA) were grafted onto nylon 6, cellulose triacetate, cotton, viscose rayon, and polyester fibers, and the stereoregularities of the grafted polymers were determined. The graft polymerization was carried out with preirradiation techniques using γ-rays from a Co 60 source. The grafted copolymers were then separated from the homopolymers by Soxhlet extraction. The grafted (branch) polymers were isolated from the trunk polymers by acid hydrolysis and their stereoregularity was determined with a 100 MHz NMR spectrometer. The stereo-regularity of PMAA or PMMA grafted onto viscose rayon or cotton fiber was different from that of the polymers formed in ordinary radical polymerization.     

Modification of partially carboxymethylated cotton via crafting with acrylic acid and styrene using gamma radiation

Partially carboxymethylated cottons (PCMC) having 15.549, 27.409, and 46.834 meq ? COOH/100 g cellulose as well as untreated cotton and alkali-treated cotton, which was prepared in an analogous manner to PCMC but, in the absence of monochloroacetic acid, were graft-copolymerized with either acrylic acid or styrene using gamma radiation under different conditions. Moisture regain and dyeing properties of the copolymers so obtained were investigated. It was found that the graft yeld increases by increasing monomer concentration and radiation dose irrespective of the monomer or substrate used. Using water/methanol mixtures as polymerization media are advantageous for grafting of styrene onto the substrates in question. The graft yields of PCMCs are much lower than those of unmodified and alkali-treated cottons when they were grafted with acrylic acid. In case of styrene on the other hand, the graft yields for PCMCs are higher than the corresponding yields obtained with the unmodified and alkali-treated cottons. Poly(acrylic acid)–PCMC graft copolymers show much higher moisture regain than PCMCs particulary when the carboxylic groups of the graft were in the sodium form. The opposite holds true for polystyrene–PCMC graft copolymers which exhibit much lower moisture regain as compared with PCMCs. The color strength of PCMC dyed with direct or reactive dyes decreases significantly after being copolymerized with poly(acrylic acid) prior to dyeing. On the other hand, this copolymerization improves the affinity of PCMCs for the basic dye and brings about perceptible shade. Polystyrene–PCMC graft copolymers acquire higher color strength than the PCMC when dyed with direct, disperse, and basic dyes but lower color strength upon dyeing with the reactive dye. Also reported were the moisture regain and dyeability of unmodified and alkali-treated cotton before and after copolymerization with acrylic acid or styrene for comparison.     

Novel regenerable N‐halamine polymeric biocides. II. Grafting hydantoin‐containing monomers onto cotton cellulose

A novel cyclic‐amine monomer, 3‐allyl‐5,5‐dimethylhydantoin (ADMH) was synthesized with good yield by the reaction of allyl bromide with 5,5‐dimethylhydantoin (DMH), and was characterized by FTIR and ¹H‐NMR spectra. ADMH alone cannot be grafted onto other polymers. However, the presence of acrylonitrile markedly enhanced the ADMH graft yield onto cotton cellulose. The influence of reaction conditions on the graft copolymerization was investigated. After chlorine bleach treatment, hydantoin units in the grafted copolymers were easily transformed into N‐halamine structures. Grafted samples exhibited potent antibacterial activity against Escherichia coli, and the functional properties were shown to be durable and regenerable. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 617–624, 2001     

Graft copolymerization of methyl acrylate onto cellulose initiated by potassium ditelluratoargentate(III)

A novel redox system, potassium ditelluratoargentate(III) (DTA)–cellulose, was employed to initiate the graft copolymerization of methyl acrylate onto cellulose in alkali aqueous solution. Grafting parameters, such as total conversion, grafting efficiency and grafting yield, were evaluated comparatively. The dependence of these parameters on temperature, reaction time, initiator concentration and ratio of monomer to cellulose was also investigated. Graft copolymers with high grafting parameters were obtained, which indicated that the DTA–cellulose redox pair is an efficient initiator for cellulose grafting. The proof of grafting was obtained from gravimetric analysis and infrared spectra. A tentative mechanism involving a two‐step single‐electron‐transfer process of DTA is proposed to explain the generation of radicals and initiation. Thermogravimetry, X‐ray diffraction and scanning electron microscopy were also carried out to study the thermal stability, crystallinity and morphology of the grafted copolymers. Copyright © 2004 Society of Chemical Industry     

Graft copolymers prepared by atom transfer radical polymerization (ATRP) from cellulose

A cellulose-based macro-initiator, cellulose 2-bromoisobutyrylate, for atom transfer radical polymerization (ATRP) was successfully synthesized by direct homogeneous acylation of cellulose in a room temperature ionic liquid, 1-allyl-3-methylimidazolium chloride, without using any catalysts and protecting group chemistry. ATRP of methyl methacrylate and styrene from the macro-initiator was then carried out. The synthesized cellulose graft copolymers were characterized by FTIR, ¹H NMR and ¹³C NMR spectroscopies. The grafted PMMA and PS chains were obtained by the hydrolysis of the cellulose backbone and analyzed by GPC. The results obtained from these analytical techniques confirm that the graft polymerization occurred from the cellulose backbone and the obtained copolymers had grafted polymer chains with well-controlled molecular weight and polydispersity. Through static and dynamic laser light scattering and TEM measurements, it was found that the cellulose graft copolymer in solution could aggregate and self-assembly into sphere-like polymeric structure.     

Characterization of products prepared by homogeneous grafting of styrene onto cellulose in a sulfur dioxide–diethylamine–dimethyl sulfoxide medium

Homogeneous graft copolymerization of styrene onto cellulose was carried out using a SO₂–DEA–DMSO cellulose solvent reaction medium and γ-ray mutual irradiation. The yield of grafted side chain polymer and the homopolymer in this reaction system proved to be polysulfone, a styrene–sulfur dioxide copolymer in which the number of sulfur atoms per polymer chain is 3–3.5. Several characterizations of the graft product were attempted. The graft products were extracted with boiling benzene for 24 hr to remove homopolymer, and then the cellulose backbones were hydrolyzed. After hydrolysis, the polysulfone residues were separated by thin-layer chromatography (TLC) into two components, i.e., attendant homopolysulfone and the true side chain polysulfone having some sugar residues at one of the polymer chain ends. The weight fraction of these components for each graft product was determined by a TLC scanner. The molecular weight of the side chain polysulfone remained constant and significantly lower than that of the homopolysulfone throughout the reaction period. By assuming that no scission of cellulose chains occurred throughout the graft reaction, the number of branches per starting cellulose molecule was assessed to be surprisingly large, ranging from 2.4 to 10.6 at a total dose of 1–8 mR of irradiation. It was also found that percent grafting increased with irradiation time because of an increase in the number of branches per cellulose chain. Furthermore, we succeeded in separating the graft product into ungrafted cellulose and the true graft copolymer containing a small amount of attendant hompolysulfone.     

Graft copolymerizations of modified cellulose,grafting of acrylonitrile,and methyl methacrylate on carboxy methyl cellulose

Graft copolymers of acrylonitrile (ACN), methyl methacrylate (MMA), and their mixtures on carboxy methyl cellulose (d.S 0.4–0.5) were prepared by the use of ceric ion initiator in aqueous medium. The graft copolymers were characterized by IR spectroscopy. The extent of graft copolymerization of ACN and MMA was measured in terms of graft level, molecular weight of grafted polymer chains, and the frequency of grafting as functions of ceric ion concentration. It was found that at comparable reaction conditions, the molecular weight of the grafted polymer chains and the frequency of grafting were not of the same order of magnitude. For the monomer mixtures, the copolymer compositions obtained from the total nitrogen contents of the copolymer samples showed that a disproportionately low amount of ACN monomeric units were incorporated into the graft copolymer, even at high ACN content of the feed. © 1996 John Wiley & Sons, Inc.     

Preparation of cellulose graft copolymers having polypeptide side chains and their blood compatibility

Blood compatibility of cellulose graft copolymers with poly(γ-benzyl-L -glutamate) and poly(N⁵-2-hydroxyethyl-L -glutamine) (Cell-g-PBLG and Cell-g-PHEG) was examined in vivo blood tests. For this purpose, Cell-g-PBLG graft copolymers with PBLG contents ranging from 7 to 60 mol % were prepared by polymerizing N-carboxy-γ-benzyl-L-glutamate(γ-BLG NCA) using aminoethyl cellulose (AE-Cell) with degree of substitution of 0.05 as macroinitiator. Graft copolymerization was carried out under a variety of conditions at 20°C in dimethyl-sulfoxide. Monomer conversion higher than 60% were obtained for all the polymerization runs. The solubility tests revealed that all of the AE-Cell and the polypeptides formed were grafted. The Cell-g-PHEG graft copolymers were prepared by treating Cell-g-PBLG graft copolymers with 2-amino-1-ethanol. Characterization of these graft copolymers were carried out by IR spectroscopy, DSC, and water content measurement. Tests for blood compatibility, in vivo, were made by a method of peripheral vein indwelling suture which was developed by one of the authors. The coating of graft copolymers on the polyester suture was made by casting either from formic acid solution of LiCl/dimethylacetamide solutions using water as the regenerating medium, and the polymer-coated sutures were implanted into a jugular and femoral vein of a dog. The results showed that the graft copolymers examined have excellent antithrombogenic properties.     

Grafting cellulose acetate with styrene maleic anhydride random copolymers for improved dimensional stability of cellulose acetate

Graft copolymers of cellulose acetate (CA, d.s.:2.45) with styrene maleic anhydride random copolymers (SMAs) were synthesized by reacting the hydroxyls on CA backbone with the anhydride on SMA. The formation of graft copolymers leads to compatibilized blends with microscopic phase domains under appropriate conditions. The grafting reaction was studied in detail. The uniform dispersion of SMA in the CA matrix brings new properties to the grafting reaction products. Tests from acetone-cast films showed improved dimensional stability in comparison to cellulose acetate; i.e., in the presence of 50% SMA in the formulation, there is more than 50% reduction on the dimensional change as compared to CA. The dimensional stability of the grafting products is better or comparable to cellulose triacetate. There are, for the alloys, reduced moisture adsorption, improved tensile strength, tensile modulus, reduced elongation, as compared to cellulose acetate. © 1994 John Wiley & Sons, Inc.     

Free-radical grafting of cellulose in N-methylmorpholine oxide: Water-soluble pam-g-cellulose copolymers

The homogeneous graft copolymerization of acrylamide (AM) onto cellulose initiated by t-butylperoxy-2-ethylhexanoate in a cellulose solvent, N-methylmorpholine oxide (NMMO), was investigated. The method afforded water-soluble PAM-g-cellulose copolymers in fair yields. The copolymers produced are of low molecular weight (50,000–100,000 M?_w). Little apparent homopolymerization was observed.     

Radiation-induced graft copolymerization of mixtures of styrene and acrylamide onto cellulose acetate. VI. Permeability of sodium chloride and sodium sulfate

Acrylamide, styrene, and mixtures of acrylamide and styrene were grafted onto cellulose acetate film. The permeabilities of sodium chloride and sodium sulfate through the ungrafted and grafted cellulose acetate films were studied. Permeability increases with the increase in the extent of grafting of acrylamide; whereas it decreases with the increase in the extent of grafting of styrene onto cellulose acetate. The same trend in permeability was observed when cellulose acetate was grafted with the binary monomer mixture. Permeability is also found to depend on the nature of the solute dissolved in water. The results were discussed in terms of free volume concept of the water-swollen films.     

Preparation,characterization, and properties of cellulose–polyacrylamide graft copolymers

Graft copolymers of acrylamide on cellulose materials (α‐cellulose 55.8%, DP 287.3) obtained from Terminalia superba wood meal and its carboxymethylated derivative (DS 0.438) were prepared using a ceric ion initiator and batch polymerization and modified batch polymerization processes. The extent of graft polymer formation was measured in graft level, grafting efficiency, molecular weight of grafted polymer chains, frequency of grafting as a function of the polymerization medium, and initiator and monomer concentrations. It was found that the modified batch polymerization process yielded greater graft polymer formation and that graft copolymerization in aqueous alcohol medium resulted in enhanced levels of grafting and formation of many short grafted polymer chains. Viscosity measurements in aqueous solutions of carboxymethyl cellulose‐g‐polyacrylamide copolymer samples showed that interpositioning of polyacrylamide chains markedly increased the specific viscosity and resistance to biodegradation of the graft copolymers. The flocculation characteristics of the graft copolymers were determined with kaolin suspension. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 913–923, 2003