Radiation-induced graft copolymerization of mixtures of styrene and n-butyl acrylate onto cellulose and cellulose triacetate

Mixtures of styrene and n-butyl acrylate of various compositions were grafted onto cellulose and cellulose triacetate fibers preirradiated with γ-rays at 0°C in air. Monomer reactivity ratios of the grafted copolymers were found to be different from those of the nongrafted copolymers or those of AIBN-initiated copolymers. The active species initiating the graft copolymerization were trapped radicals for cellulose and peroxides for cellulose triacetate. Kinetic investigations of the graft copolymerization of styrene onto preirradiated cellulose triacetate fibers were also carried out, and it was found that the kinetic scheme for radical polymerization is also applicable to graft copolymerization in a heterogeneous system.     

Studies in the graft copolymerization of vinyl monomers on cellulosic materials

Graft copolymerization of acrylonitrile, methyl methacrylate, and vinyl acetate on bleached holocellulose initiated by ceric ions in aqueous medium was studied at 29°C. The extent of graft copolymer formation was poly(methyl methacrylate) > polyacrylonitrile > poly(vinyl acetate), indicating the influence of polarity of monomer on graft copolymerization. It was found that, although the molecular weights of the grafted polyacrylonitrile copolymer were lower than the values obtained for poly(methyl methacrylate), the latter was less frequently incorporated on the cellulosic backbone polymer than the polyacrylonitrile grafts. The marked reductions in graft level associated with thiolation of the cellulosic material suggest that hydrogen abstraction reactions from carbon atom carrying hydroxyl groups may not be important in graft copolymer formation.     

Grafting acrylonitrile and acrylic acid monomers on cellulosic materials

Graft copolymers of acrylonitrile and of acrylic acid monomers on cellulosic materials were obtained by use of ceric ion initiator in aqueous medium at a 50% (w/w) cellulose-monomer ratio. The variations of poly(acrylonitrile) grafts and of the efficiency of grafting with ceric ion concentration, and of poly(acrylic acid) grafts with temperature are examined. The dependence of water retention capacity of the grafted fibers with the graft level is reported.     

Synthesis and properties of graft copolymer of cellulose diacetate with poly(caprolactone monoacrylate)

Cellulose diacetate grafting poly(caprolactone monoacrylate) copolymers (CDA‐g‐PCLA) were synthesized by a two‐step reaction of cellulose diacetate (CDA) with poly(caprolactone monoacrylate) (PCLA). The isocyanate‐terminated intermediate (NCOPCLA) was prepared and grafted onto cellulose diacetate chains. The results of the structure analysis indicated that PCLA was connected to CDA by chemical bonding. The flow temperature of graft copolymers was lower than that of the pure CDA and decreased with increasing the grafting percentage. Outdoor soil burial tests and active sludge tests indicated that the graft copolymers have good biodegradability in natural conditions. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 85–90, 2003     

Graft copolymerization of vinyl monomers on modified cottons,XXI. Cu++/hydrazine hydrate redox system induced grafting of methyl methacrylate on periodate oxidized cellulose

Periodate oxidized cellulose was grafted with methyl methacrylate using hydrazine hydrate in presence and absence of Cu⁺⁺. The grafting reaction was favoured in presence of Cu⁺⁺ and it was advantageous to treat first the cellulose material with copper sulphate solution rather than to incorporate it in the polymerization system. The graft yields depended upon the concentrations of copper sulphate and hydrazine hydrate, pH, temperature, and time of polymerization as well as degree of oxidation of cellulose. There were optimal concentrations of copper sulphate (6–8 mmol/l) and hydrazine hydrate (2 mmol/l). A polymerization medium of pH 6 and a temperature of 60°C constituted to optimal pH and temperature for grafting. Oxidized cellulose proved to be more amenable to grafting as compared with unoxidized cellulose and the magnitude of grafting relied on the degree of oxidation. A tentative mechanism was also suggested for grafting of cellulose substrates with a vinyl monomer using a Cu⁺⁺-hydrazine hydrate redox system.     

Block/graft copolymer synthesis via ceric salt

Acrylamide and acrylonitrile were polymerized with water-soluble organic reducing compounds containing hydroxy groups such as methyl cellulose (MC), methyl hydroxy-propyl cellulose (MHPC) and poly(ethylene glycol)s (PEG) in the presence of Ce(IV) in order to produce graft/block copolymers. The effect of cerium(IV) concentration, temperature, time and monomer concentration on the yield was studied. Copolymers of cellulose derivatives and polyacrylonitrile showed solubility properties similar to polyacrylonitrile. Both cellulose derivative-polyacrylamide and poly(ethylene glycol)-polyacrylamide copolymers were soluble in water.     

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.     

Water-soluble polymers as retention aids in a model papermaking system. IV. Some block and graft copolymers

In an attempt to relate the retention behavior of water-soluble polymers in paper formation from cellulose fibers and titanium dioxide, several copolymer types were synthesized. These were acrylamide–acrylonitrile random copolymers; block copolymers of acrylamide, acrylonitrile, and 2-vinylpyridine with poly(ethylene oxide); and acrylamide graft copolymers of ethyl hydroxyethyl cellulose. Good retention and heteroflocculation behavior is shown only by the first of the above types of copolymers. Generally speaking, block copolymeric structures synthesized were of molecular size too small to act as good retention aids, although in a number of cases their performance was noticeably superior to that of the homopolymer analog. Adsorption isotherms are also reported and the overall results discussed in terms of a polymer bridging mechanism of heteroflocculation.     

Thermal behavior of cellulosic graft copolymers. II. Cotton grafted with binary mixtures of vinyl acetate and methyl acrylate

Thermal degradation of cotton, mercerized cotton, cotton grafted with vinyl acetate-methyl acrylate mixtures at different compositions, and mercerized cotton grafted with vinyl acetate–methyl acrylate mixture at a composition of 60 : 40 has been investigated using the techniques of thermogravimetric analysis (TGA) and differential thermal analysis (DTA) in nitrogen. The kinetic parameters E, n, and A have been obtained following several methods of thermogravimetric analyses. The mercerization shows a little effect upon thermic properties of cotton cellulose, making cotton thermally more stable. Graft copolymerization of vinyl acetate-methyl acrylate mixture makes cotton thermally less stable if the composition of the copolymer grafted is 100, 90, and 70 mol % VA, while in the case of cellulose graft copolymers with compositions of VA–MA of 80 : 20, 20 : 80, 5 : 95, and 0 : 100 the thermal stability is higher than that of original cotton. The thermal stability of the mercerized cotton grafted with vinyl acetate-methyl acrylate mixture with a composition of 60 : 40 depends on the percent grafting yield. The thermal stability of mercerized cotton grafted with the monomer mixture is higher than that of cotton grafted with that monomer mixture. The degradation of cellulose and cellulose graft copolymers is complex as is shown by DTA thermograms and kinetic parameters.     

Synthesis and applications of reactive carbohydrates. IV. Reactive finishes based on CMC and oxidized CMC copolymers

Carboxymethyl cellulose (CMC) and persulfate-oxidized CMC samples were assessed for acidic and reducing properties before and after graft copolymerization with acrylamide using K₂S₂O₈ as initiator. The acidic properties were expressed as milliequivalents of carboxyl groups/100 g CMC while the copper number was taken as a measure for the reducing properties. Results obtained signify that increasing the duration of persulfate oxidation from 15 to 60 min causes a significant enhancement in the carboxyl content of CMC particularly during the first 50 min of oxidation. The same holds true for the copper number, but no further significant enhancement could be observed after 30 min. The copolymerization reaction decreases substantially the acidic and reducing groups of the CMC substrates examined. The results showed also that oxidation of CMC increases its susceptibility toward grafting: The higher the extent of oxidation, the higher the extent of grafting. Methylolation of the polyacrylamide–CMC graft copolymers results in reactive finishes. The latter were applied either alone or together with etherified methylolated melamine to cotton fabric samples according to the conventional pad–dry–cure method. The treated samples withstand severe washing, suggesting the occurrence of chemical bonding between the methylolated CMC products and cotton.     

Effect of degradative treatments on cotton graft copolymers. Part IV. Hydrolytic susceptibility of poly(acrylonitrile)-cotton graft copolymers

Acrylonitrile (AN) was graft polymerized to different levels onto cotton fabric using ferrous cellulose thiocarbonate-hydrogen peroxide redox system. The hydrolytic susceptibility toward 0.5 N HCl at 40°, 60°, and 80°C for 15–90 minutes of copolymers having 12, 15, and 22.5% graft was studied and compared with those of ungrafted and initiator-treated cottons. Hydrolytic susceptibility was assessed by monitoring carboxylic groups, copper number, nitrogen content (in the case of the copolymers) and tensile strength of the five substrates. Results obtained concluded that poly(AN)-cotton graft copolymers were more susceptible to acid degradation than the ungrafted and initiator-treated cottons when the acid treatment was performed under mild conditions. On the other hand, they were less susceptible when the acid treatment was carried out under relatively severe conditions.     

ESR studies of the photodegradation of cellulose graft copolymers

Ultraviolet light induced free radicals in cellulose and cellulose graft copolymers were studied by means of ESR spectroscopy. At least six kinds of free radicals were formed in cellulose when the polymer was irradiated with ultraviolet light. Polystyrene and poly(methyl methacrylate) are more resistant to ultraviolet light than cellulose; however, the cellulose graft copolymers of polystyrene and poly(methyl methacrylate) were degraded by ultraviolet light. ESR studies revealed that photoinduced free radicals in cellulose graft copolymers were formed at the grafting branches of the copolymers rather than the cellulose backbone. The mechanisms of light stabilization and energy transfer reactions of cellulose and cellulose graft copolymers are discussed.     

双亲性氯化聚乙烯接枝共聚物的吸水膨胀性能

采用反相悬浮法制备了颗粒状接枝共聚物———氯化聚乙烯接枝丙烯酸(CPE-g-AA)、氯化聚乙烯接枝丙烯酰胺(CPE-g-AM)和氯化聚乙烯接枝混合单体丙烯酸、丙烯酰胺[CPE-g-(AA-AM)],并通过热压法制得接枝共聚物片材。考察了颗粒状接枝共聚物和接枝共聚物片材的吸水膨胀性能。结果表明,接枝共聚物的吸水性能与接枝单体的种类及其接枝率有关,相同接枝率的CPE-g-AA的吸水量比CPE-g-AM的大。当混和单体丙烯酸/丙烯酰胺的质量比为2/2时,所得接枝共聚物的抗盐性能最好。接枝共聚物片材可反复吸水膨胀,接枝率为62%的CPE-g-AA片材的二次吸水达到平衡时的吸水率和膨胀率分别为120%和41%。通过测定接枝共聚物的接触角表明,CPE-g-AA对水的润湿作用比CPE-g-AM明显。     

Effect of degradative treatments on cotton graft copolymers. Part V. Behavior of poly(acrylamide)-cotton graft copolymers toward acid treatments

Polyacrylamide (Aam)-cotton graft copolymers having 9, 14.5, and 20% graft were synthesized using ferrous cellulose thiocarbonate-hydrogen peroxide redox system. These copolymers as well as ungrafted and initiator-treated cottons were subjected to acid treatments (0.5 N HCl) at 40°, 60°, and 80°C for 15-90 minutes. Hydrolytic susceptibility of the five substrates was assessed by monitoring carboxylic groups, copper, number, nitrogen content (in case of the copolymers), and tensile strength. Results obtained concluded that the copolymers exhibit higher resistance to acid hydrolysis than the ungrafted and initiator-treated cottons. This was explained in terms of involvement of the ? CONH₂ groups of the graft in an interaction with HCl.     

Graft polymerization of some vinyl monomers onto acrylic rubber. II. Mechanical properties of graft polymers

Some mechanical properties of styrene and acrylonitrile copolymers grafted onto acrylic rubber are investigated. The impact strength of graft polymers depended upon the nature and the concentration of the catalyst, the composition and the intrinsic viscosity of the rubber, and the acrylonitrile content in the rigid matrix. The most desirable result was obtained when benzoyl peroxide as the catalyst, n-butyl acrylate–acrylonitrile copolymer of 7–10% acrylonitrile content, and about 0–5% acrylonitrile in the rigid matrix were used. Dynamic mechanical tests show the increase in efficiency of rubber modification by the grafted chains. The better weathering resistance of these graft polymers, as compared with commercial ABS plastics, was confirmed.     

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 of partially hydrolysed poly(methyl methacrylate) onto mesylated cellulose acetate

A new synthetic route to cellulose graft polymers by nucleophilic displacement of mesylate groups from mesyl cellulose acetate (MCA) by the polystyrylcarboxylate anion has been recently reported by us. This approach to cellulosic graft polymers overcomes the drawbacks of the radical polymerization methods and allows for precise control of parameters such as the molecular weight and molecular weight distribution of the grafted side chains, higher degree of substitution on the cellulose backbone, the number and nature of grafted side chains and overall better control and reproducibility of the grafting process. In this report, partially hydrolysed poly(methyl methacrylate) was successfully grafted on to mesylated cellulose acetate in excellent yields by nucleophilic displacement of mesylate groups in less than 60 min at 75°C.     

Graft copolymerization of vinyl monomers with modified cotton. II. Grafting of acrylonitrile and methyl methacrylate on acetylated cotton

Ce(IV)-induced polymerization of acrylonitrile and methyl methacrylate with acetylated cotton having different acetyl contents was investigated. The extent of interaction between the cotton and monomer is dependent upon the acetyl content of the former as well as on the reaction conditions. Increasing the acetyl content caused a significant decrease in the graft yield. Increasing the acrylonitrile concentration was accompanied by a substantial increase in the graft yields. The same effect was found with the initiator up to a certain concentration, but beyond it there was a reversal. The rate of grafting increased by rising the temperature and follow the order 60° > 40° > 30°C. The Ce(IV) consumption during grafting is greater than that consumed during oxidation. The consumption of Ce(IV) by the cellulosic materials was favorably influenced by the concentrations of monomer and initiator, time, and temperature. Rates of grafting and Ce(IV) consumption during oxidation of acetylated cottons having different acetyl contents strongly support the postulated mechanism of grafting using the Ce(IV)–cellulose redox system. Ce(IV) oxidation had practically no effect on the acetyl groups (expressed as per cent combined acetic acid) of the modified cotton.     

Synthèse et caractérisation de copolymères cellulose–poly(méthacrylate de méthyle): Greffage par le système acide de Caro–ion Fe3+

Methyl methacrylate was grafted onto cellulose using Caro's acid-Fe³⁺ system as initiator. The effect of grafting time, ferric ion concentration, and cellulose/monomer ratio, on the per cent grafting, was investigated. From studies of the reaction mechanism with model compounds it was postulated that the grafting did not occur at the 1,2-glycol units or at the hemiacetal unit in the end of the cellulose molecule. Concurrent degradation of the cellulose during the graft copolymerization was examined. A linear relationship between the per cent grafting and the number of cellulosic broken chains by hydrolysis was found, from which it would seem that the structure of the graft copolymer was of block-type. The structure of the graft copolymers was also studied by determination of the molecular weights of the grafted PMMA branches, after hydrolysis of the cellulosic backbone. In all cases, independently of reaction conditions, the molecular weights of the grafted branches were very high and their number low. The number of graft branches per cellulose chain was calculated from the per cent grafting, the molecular weights of the PMMA branches and of the cellulosic backbone. This number was compared with the number of cellulosic bonds broken during grafting.