Grafted Side Chains Research Articles

The effect of vinyl monomer grafting on the water sorption kinetics and equilibria in cellulose

AbstractWood pulp cellulose was grafted with styrene and a number of other vinyl monomers using the mutual radiation technique. The effects of the level of grafting, type of monomer, and the grafting conditions on the water sorption equilibria and kinetics were determined. Styrene was studied in considerable detail. Styrene grafting reduced the equilibrium water content but water diffusivities increased as a consequence of styrene grafting. Conversely, the grafting of polar monomers such as acrylonitrile, ethyl acrylate, and acrylic acid led to somewhat higher water regains but to decreased diffusion constants.The swelling conditions used during the mutual grafting process with styrene significantly affected the grafting rates and the properties of the resulting grafts. For example, the equilibrium water contents at the same level of grafting, was a function not only of percent graft but also of the specific swelling conditions. These moisture regains were inversely related to the density of the grafted fibers. These results are discussed in terms of the conformation of the grafted side chains which is determined by the various grafting conditions.

Anionic graft polymerization of propylene sulfide on cellulose. I

AbstractThe anionic graft polymerization of propylene sulfide on cellulose membrane was studied. Alkali cellulosates were used to initiate graft polymerization, and graft polymers of high polypropylene sulfide content were obtained in good yields. The graft polymerization was accompanied by a certain extent of homopolymerization. The effects of reaction solvent, monomer concentration, cellulosate degree of substitution, and type of the alkali metal cellulosate on the graft polymer composition, yield, and on the molecular weight of the grafted side chains were investigated.

GRAFT COPOLYMERIZATION OF METHYL METHACRYLATE ONTO CELLULOSE ACRYLATE ACETATE

Cellulose acrylate acetate, which has double bonds in the side chain, was synthesized and methyl methacrylate was grafted onto the cellulose ester in the homogeneous systems using benzoyl peroxide as an initiator and dioxane or cyclohexanone as a solvent.The following results were obtained:1) Grafting efficiency was low and was 28.1% at the most. The values at 80°C were larger than at 60°C. At 80°C the grafting in dioxane as a solvent resulted in a higher degree of grafting compared to that in cyclohexanone, but no difference was observed among solvents at 60°C.2) The formation of homopolymer was larger at 80°C than at 60°C, and no difference was observed among solvents.3) Although the reaction was carried out in the homogeneous systems, in which both the trunk polymer and the graft copolymer were dissolved, a number of grafted side chains per trunk polymer was less than unity irrespective of the reaction conditions. This is supposingly attributed to the difficulty of the attack on initiator and propagating polymer radicals on double bonds in the cellulose esters due to the steric hindrance of acetyl groups existing in the cellulose ester, and consequently the smaller reactivity of double bonds in this cellulose ester.4) The graft copolymerization was also carried out using cellulose acetate instead of cellulose acrylate acetate under the same reaction conditions. Almost the same amount of homopolymer was obtained as in the case of cellulose acrylate acetate, but no graft copolymerization occurred. Accordingly, the double bond in acryloyl group was definitely involved in the reaction.5) The grafted side chains could be perfectly isolated from the graft copolymers by hydrolyzing the trunk polymer for 12 hours at 105°C using a dioxane-HCl system which can dissolve both the graft copolymer and the side chain polymer.

Anionic graft polymerization of methacrylonitrile on potassium starch alkoxide

AbstractThe anionic graft polymerization of methacrylonitrile on potassium starch alkoxide in dimethyl sulfoxide was studied. Factors affecting the graft polymerization such as monomer and alkoxide concentrations as well as temperature were investigated. The yield of the graft polymers was found to increase with alkoxide concentration, and it was possible to incorporate all the starch into graft polymer. On increasing the monomer concentration the graft polymer yield increased to a flat maximum. At the higher monomer concentrations, the efficiency of monomer in giving graft polymer decreased due to increased homopolymer formation. The composition of the graft polymers varied with increasing monomer concentration, graft polymers having about 40–65% of grafted starch were obtained. With increasing temperature (10 to 60°C), the yield of graft polymer decreased, there was more homopolymerization, but the amount of starch incorporated in the graft remained constant. The structure of the graft polymers was deduced from hydrolysis of the starch backbone of the graft polymers by dilute mineral acid and the determination of the molecular weights of the grafted side chains, and from oxidation by periodic acid, which showed the extent of grafting at the secondary hydroxyl groups. These results have shown that by anionic graft polymerization it is possible to obtain graft polymers having more densely packed grafted side chains of relatively low molecular weights than those obtained previously by free‐radical graft polymerization.

Anionic graft polymerization of ethylene oxide on starch. II. Structure of the graft polymers

AbstractStarch–poly(ethylene oxide) graft polymers were prepared in DMSO at various monomer and starch alkoxide concentrations. Complimentary and varied information on the structure of the graft polymers was obtained from NMR and periodic acid oxidation of the polymers. From the NMR spectra of the graft polymers in pyridine containing a trace of HCl, which causes shifting of the resonance of the internal CH2O protons from the terminal CH2OH protons, the polyethylene oxide content, the DPn of the grafted side chains, and the efficiency of the alkoxides were calculated. With increase of the alkoxide concentration there was a small decrease in DPn, and in the efficiency of the alkoxides in initiating graft polymerization. With increase of monomer concentration, there was only a small increase in DPn but a large increase in the efficiency, indicating the existence of transfer reactions between the growing anions and the free hydroxyl groups on the starch. The results of he periodic acid oxidation showed that with increase of alkoxide concentration there was no significant change in the per cent oxidation of the graft polymers, but with increase of monomer, there was an increase in the participation of the secondary hydroxyl groups in initiation. This supports the NMR evidence for the existence of transfer reactions leading to DPn values much lower than those calculated from [monomer]/[catalyst] ratios.

Anionic graft polymerization of 4-vinyl pyridine on starch and dextrin

The anionic graft polymerization of 4-vinyl pyridine on the potassium alkoxide derivative of starch or dextrin in dimethyl sulphoxide solution was studied. Graft polymerization occurred only at relatively high alkoxide concentration. The yields of pure graft polymer were low due to extensive homopolymerization, probably caused by chain transfer to the acidic hydrogen of the monomer. The grafted side chains of poly-4-vinyl pyridine were detached from the carbohydrate backbone by acid hydrolysis, and their molecular weights were found to increase with monomer concentration in accordance with a “living” polymerization. The results obtained in the graft polymerization on starch and dextrin were similar.

Effect of nitrobenzene in the styrene–cellulose acetate graft polymerization system

AbstractThe effect of nitrobenzene, a polymerization retarder, upon the direct γ‐ray‐induced graft polymerization of styrene onto pyridine‐swollen cellulose acetate film was studied. When the films were not highly swollen, small nitrobenzene additions caused an increase in the amount of grafted polystyrene and grafted cellulose acetate. However, when the substrate was highly swollen, nitrobenzene additions reduced the amount of grafted polystyrene without pronounced changes in the amount of grafted cellulose acetate. The number‐average molecular weights of the grafted side chains were always two to three times those of the homopolystyrene formed in the bulk monomer solution, which is indicative of hindered chain termination within the substrate film under all reaction conditions. Nitrobenzene additions prevented polystyrene crosslinking reactions, probably because the termination reactions in the presence of nitrobenzene occur by disproportionation rather than by coupling of chain ends. Viscometric results indicated that the polystyrene side chains were branched.

The preparation and characterization of some cellulose graft copolymers. V. ESR study of preirradiation grafting of styrene to cellulose acetate

AbstractPrevious studies have shown a two‐peak molecular weight distribution of the grafted polystyrene side chains from preirradiation‐grafted cellulose acetate. ESR has been used to investigate this grafting system in further detail. It was found that the rate of decay of the trapped radicals on adding the monomer solution was quite slow and a substantial proportion remained after 3 days at 25°C. The G value for radicals lost was, however, in good agreement with the G (grafted side chains) produced during the same period. The ESR spectrum does not change on addition of the monomer solution. The explanation offered is that the side chains grow and terminate rapidly compared with the slow overall rate of decay. The grafting yield and the molecular weight of the grafted side chains continue to grow until the reaction is terminated, leading perhaps to the high molecular weight narrow distribution fraction.

THE SYNTHESES OF α, β-UNSATURATED CARBOXYLIC-ACETIC MIXED CELLULOSE ESTERS AND THEIR UTILIZATIONS

Acrylic-acetic acid and vinylacetic-acetic acid mixed cellulose esters were synthesized, and styrene and methyl methacrylate were grafted onto them with benzoyl peroxide as a catalyst. The results obtained are as follows:1) The rate equations of graft polymerization were composed of two first order reactions. It is infered that after the gel polymers are formed, the rate of grafting is determined by the rate of diffusion of monomers into the gel polymers (Fig. 2)2) The degree of grafting varies with the state of cellulose mixed esters and increases in the following order; film, swollen film and homogeneous solution. (Table 3)3) The grafted side chains are isolated from the grafted polymers by hydrolyzing the trunk polymers for 72 hrs at 105°C with 5 N HCl. But the yield of the acid hydrolysis depends greatly on the degree of grafting. Generally, isolation of PMMA side chains is easier than those of PSt. (Fig. 3)4) Average number of grafted side chains per a trunk cellulose molecule was 0.13-3.71, which is the same as that reported previously for the graft copolymerization by ceric salt catalyst. (Fig. 3, Table 5)5) Gel polymers are formed during polymerization by crosslinking reaction through PSt or PMMA radicals and not by the direct crosslinking reaction between the cellulose esters.

MODIFICATION OF SYNTHETIC FIBER BY THE GRAFT COPOLYMERIZATION OF REACTIVE MONOMER

Acrylic acid was graft copolymerized onto polypropylene fiber and fabric using Co60 γ-ray preirradiation method.As the grafted polypropylene has reactive groups such as caroboxyl groups in the grafted side chains, some aftertreatments including cross-linking can be achieved using these reactive groups.Some properties of the acrylic acid grafted and aftertreated polypropylene fiber and fabric were examined.The results are summarized as follows:(1) Tensile properties such as dry, wet and knot tenacity and elongation of the grafted and aftertreated fibers are equal to that of original polypropylene fiber.(2) Heat shrinkage of the fibers decreases considerably by acrylic acid grafting and the fiber grafted by 62% shows heat shrinkage of 5_??_7% and does not melt till 300°C.(3) The effects of aftertreatment of the grafted fiber on the heat shrinkage are also remarkable. For example, greater heat stability is obtained by Ca-salt, NH4Cl and epoxy treatments. Melting temperature of the polypropylene monofilament is not improved by acrylic acid grafting, but elevates to as high as above 300°C by the aftertreatment with inorganic salts of some metals such as Na and Ca.(4) Tensile properties of the grafted and aftertreated fibers at elevated temperature do not improve as expected from the melting property.(5) Moisture regain of polypropylene fabric increases by acrylic acid grafting and metal salts treatments. Especially in the case of Na-salt treatment the moisture regain is about 10% in the 35.8% grafted sample.(6) It was found that the polypropylene fabric which is 20.5% grafted with acrylic acid and converted into Na-salt has excellent dyeability for cationic dye and heat settability.(7) Frictional static electricity of the acrylic acid grafted polypropylene monofilament and fabric decreases to about one half of the original polypropylenes. Conversion of the grafted acrylic acid to a hydrophilic Na-salt shows more remarkable decrease of frictional static electricity.

Grafting of polypeptides on polyhydroxy polymers

The homogeneous graft polymerization of γ-benzyl- l-glutamate NCA (N-carboxy anhydride) and ε-carbobenzoxy- l-lysine NCA on cellulose acetate alkoxide was studied to discover the mechanism of the graft polymerization. It was found that the initiation reaction was that of a direct addition of the alkoxide to carbonyl no. 5 of the NCA, and proof was obtained for the existence of an ester linkage between the polypeptide side chain and the cellulose acetate backbone. The polypeptide side chains had the amino group as the characteristic end group, as determined from titration and Van Slyke determination, and their DP n was equal to [NCA] o/[alkoxide] o( A/ I). A linear relationship was found between log [η] of graft polymer vs. log A/ I, showing that DP▾ of the polypeptide side chains was proportional to A/ I. The DP w found on the cleaved polypeptide side chains was higher than A/ I, and the ratio DP w / DP n was between 9 and 23. This high ratio was due to the fact that only 4–9 per cent of the alkoxide used initiated graft polymerization of the high molecular weight polypeptide side chains, the rest of the initiator leading to grafting of amino-acid units instead of the high polypeptide chains. The effects of the solvent, the alkali metal counterion and the concentrations of reactants on the intrinsic viscosity of the graft polymers was explained by the existence of propagation through a dissociated carbamate ion-pair as postulated by Idelson and Blout. The effect of both the polymeric backbone and the grafted side chains on the viscosity of the graft polymers was investigated and correlated with the conformation of the polypeptide side chains.

CHEMICAL TREATMENT OF COTTON BY THE GRAFT COPOLYMERIZATION OF REACTIVE MONOMER, AND CROSS-LINKING

Glycidyl methacrylate was graft polymerized onto cotton by simultaneous Co60 γ-ray irradiation in the presence of air at room temperature. During the graft polymerization, epoxy rings in the grafted side chains did not open by the irradiation of the total dose below 2×105 r, but insoluble homopolymer was formed above this dose.As the grafted cotton has reactive epoxy rings in the grafted side chains, long chain cross-linkings can be introduced to the cotton cellulose using these reactive groups.The crease recovery and some tensile properties of the grafted and cross-linked cottons were examined.The results may be summarized as follows:(1) Dry crease recovery of the grafted cottons cured after treated with H3PO4-methyl ethyl ketone, HCOOH-morpholine and ethylene glycol-BF3 respectively increases considerably, but no improvement is observed in wet crease recovery.(2) Curing of the grafted cottons treated with ethylene diamine or bis (hydroxy ethyl) sulfone gives no effects on improving both the dry wet crease recoveries.(3) Curing of the grafted cottons treated with Zn(BF4)2 solution gives a considerable improvement in both the dry and wet crease recoveries.(4) Though the strength of warp of the grafted cotton fabric is decreased by cross-linking, the tensile damage of cotton by cross-linking is remarkably prevented by the grafting.

Preparation and characterization of some cellulose graft copolymers. Part III. The role of concurrent degradation during radiation grafting

AbstractThe radiation degradation of cellulose acetate has been studied both in the dry state and in solution. The rate of degradation was greater in the solid state and was unaffected by oxygen. Conjugated solvents such as pyridine, toluene, and α‐methylstyrene were shown to exert considerable protection against the radiation degradation of cellulose acetate when in solution or as swollen films. α‐Methylstyrene has been used as a model for styrene to study the amount of degradation accompanying the grafting process. Matching experiments have been carried out by using both the mutual and the preirradiation methods of grafting. Considerably greater chain cleavage was found to accompany the grafting in the preirradiation case. With both methods the number of chain cleavages has been measured when α‐methylstyrene was present in the “grafting” solution and the number of grafted side chains when styrene was used. It was shown that at least twice as many grafted chains as cleavages occur with the mutual technique, but in the case of preirradiation the number of cleavages is comparable to the number of grafted chains. The G (grafted chain) value for cellulose acetate with styrene was determined and was about 1.1 in all cases. The G (chain cleavage) values varied, however, from 0.2 to 1.3, approximately. The proportion of grafted chains attached to the ester groups was determined by extraction with benzene after cold alkaline hydrolysis. About half of the grafts were found to be attached in each case, including the preirradiation product. In general, it can be said that in every case at least 50% of the graft copolymers are side‐chain grafts; this figure is probably considerably higher in the case of the mutual radiation preparations.

Molecular weight distributions of the side chains of radiation initiated graft copolymers

The grafted side chains of cellulose acetate-polystyrene grafts have been separated from the cellulosic backbone by acid hydrolysis. The molecular weight distributions of the polystyrene resulting from a mutual and a pre-irradiation graft polymerization have been determined using a column elution technique. Both samples had unusually broad molecular weight distributions; however, whereas the mutual product had a broad single distribution, the pre-irradiation sample had a two-peak distribution and had a large amount of polymer of very narrow and very high molecular weight. Some reasons for the differences are presented.

Synthesis of graft copolymers by a transesterification method

AbstractIt is shown for the first time that mutual transesterification between carbochain polyesters (polymethyl methacrylate) and heterochain polyesters may be used for synthesizing graft copolymers. The graft copolymers obtained from polymethyl methacrylate and crystalline polyesters are crystalline have high softening temperatures. The grafting of amorphous polyesters yields amorphous graft copolymers. An increase in the number of graft side chains is accompanied by a decrease in intrinsic viscosity of the copolymer and by a rise in value of the Huggins constant. The decrease in the intrinsic viscosity is not the result of a degradation process, since polymethyl methacrylate may be regenerated by methanolysis of the graft copolymers. The intrinsic viscosity of the regenerated polymethyl methacrylate is equal to that of the initial polymer. Graft copolymers from polymethyl methacrylate and heterochain polyesters possess a lower tensile strength and higher ultimate elongation than polymethyl methacrylate. It was also established that on heating mixtures of methyl methacrylate and ω‐hydroxyacids in the presence of a catalyst graft copolymers form by simultaneous polymerization, polycondensation, and mutual transesterification reactions. Some correlations in this process and the properties of the resultant graft copolymers have been studied.

Studies on grafting glycidyl methacrylate on polyvinyl chloride backbones

AbstractGraft copolymers of glycidyl methacrylate on polyvinyl chloride backbones were prepared by the free radical technique. Three types of backbones were used: (1) vinyl chloride homopolymer; (2) copolymer of vinyl chloride–vinyl acetate, 87:13; (3) copolymer of vinyl chloride–vinylidene chloride, 89:11. The grafting reactions resulted in products with lower intrinsic viscosities than the unreacted backbones. The graft copolymers were fractionated with the separation of glycidyl methacrylate homopolymers from the rest of the graft products. Unreacted backbones were separated through gelation of all the epirane‐bearing chains. Structure proof was conducted by chemical cleavage of the grafted side chains by reduction with LiAlH4 and through acid hydrolysis.

Radiation-Induced Interaction of Acrylonitrile with Cyanoethylated Cotton

The radiation-induced interaction of acrylonitrile with cyanoethylated cotton prob ably involves grafting of side chains of acrylonitrile at the site of the cyanoethyl groups. The extent of interaction is dependent on the degree of substitution of the cotton and on radiation dosage. There are increases in delayed elastic recovery and elongation- at-break and decreases in permanent set, average stiffness, and solubility of the cellulose of the treated cottons.

Improved dyeability of polyacrylonitrile fibers by radiation grafting with vinylpyrrolidone

>Two processes are described. In one, doses of l0-60 krad are given to the polymer-aqueous monomer system at dose rates of 3-27 krad min. In the other process, 0.2-3.0 Mrad is given the system at 0.5-90 Mrad/sec, followed by a heat treatment to elongate the graft side chain. Oxygen inhibits the grafting and various inorganic salts such as sulfates and phosphates enhance the grafting. (auth)

Oxyethylation of carbochain and heterochain polyamides

AbstractCarbochain and heterochain polyamides are highly reactive compounds and may be quite easily converted to various polymer analogs, including compounds with graft side chains. We have studied the relations in the polyoxyethylation of heterochain and carbochain polyamides of various structure under different conditions. Under heterogeneous conditions the reaction takes place not only at the surface, but in the entire body of the film or fiber, although not to the same degree. On heterogeneous polyoxyethylation of heterochain polyamides graft polymers were obtained with up to 55% content of polyethylene oxide, with varying polyethylene oxide chain lengths and with different degrees of substitution of the groups. The formation of polyoxyethylated polyamides with high polyethylene oxide contents is facilitated by the use of a large excess of ethylene oxide and a lower degree of orientation of the films and fibers. In the polyoxyethylation of heterochain polyamides, as a result of crosslinking insoluble products may form which are greatly swelled in the various solvents. The branching and crosslinking of the macromolecules has been found to result from the reaction of the terminal carboxyl groups of the polyamides and the hydroxyl groups of the polyethylene oxide graft. On polyoxyethylation of polyamides not containing terminal carboxyl groups non‐cross‐linked, soluble, graft polymers are formed. In the heterogeneous polyoxyethylation of Polyacrylamide films, graft polymers with up to 65% polyethylene oxide content were obtained. In this case the reaction is also accompanied by the formation of crosslinks. In the reaction process one or both of the hydrogens of an amide group may be replaced by polyethylene oxide chains.

The preparation and properties of grafts of polycaprolactam on vinyl copolymers

AbstractThe reaction between vinyl polymers bearing reactive function (e.g., COOMe, COOH, NH2) and caprolactam should lead to the formation of grafted side chains of nylon 6 on a backbone of vinyl polymer. With styrene‐methyl acrylate (S/MA) co‐polymers in particular, the reaction initiated by water by 220–250°C. has been followed by measuring the melt viscosity, and the resultant polymers have been characterized. Combination takes place, but complication limit the extent of reation,e.g., loss of amino groups, crosslinking, inhomogeneity of the reaction melt. Soluble graft copolymers are formed only if the D.P. of the vinyl polymer is low, and the methyl acrylate content is high,e.g., 1:1 S/MA copolymers of D.P. 60 and 2:1 copolymer of D.P. 150 both give homogeneous graft copolymers. All other 1:1 and 2:1 copolymers of higher D.P. give insoluble products, because of crosslinking. For all copolymers in which the S/MA ratio is > 2:1, very little reaction occurs, and the products can be separated by solvent extraction into three fractions,viz.nylon 6, unchanged S/MA copolymer, and a graft copolymer. At high S/MA ratios, irrespective of the D.P., the two polymers are incompatible, and reaction is confined to the polyamide‐copolymer interfaces. The soluble graft copolymers were characterized by elemental and endgroup analysis, melting points, melt viscosity, soluble viscosity, and infrared spectoscopy. The interaction of styrene‐maleic anhydride and styrene‐acrylic acid copolymers with nylon 6 leads invariably to insoluble products.