Graft polymerization of acrylic monomers onto starch fractions. IV. Effect of reaction time on the grafting of butyl acrylate onto amylose

Studies were carried out on the grafting of butyl acrylate (BA) to amylose by the ceric ion method. After removing the homo-PBA with THF and toluene, and the ungrafted amylose with 0.5NNaOH, the PBA content of the graft copolymers was determined by acid hydrolysis with 1N HCl. The influence of reaction time on the grafting yields was determined and the largest values were: 82% for the grafting efficiency, 246% for the percent grafting, 62% for the grafted amylose, 48% for the grafted PBA, and 64% for the total conversion.     

Diffusion-controlled reaction. VI. Radiation graft polymerization of styrene to polyethylene

The radiation graft polymerization of styrene to polyethylene was studied under diffusion-controlled conditions of radiation intensity I, monomer concentration M₁, and polymer sample thickness L. The results of the present study together with previous work under diffusion-free conditions verify our theoretical model for the diffusion-controlled reaction. The grafting rate is inverse first order in L for diffusion-controlled reaction and independent of L for diffusion-free reaction. The order of dependence of grafting rate on radiation intensity for diffusion-controlled reaction is one-half that for diffusion-free reaction. Diffusion control leads to a decrease in the order of dependence of grafting rate on monomer concentration. The decrease is greater than theoretically predicted; possible reasons for this effect are described.     

Grafting vinyl monomers to starch by ceric ion. I. Acrylonitrile and acrylamide

Studies were carried out on the grafting of acrylonitrile (AN) and acrylamide (AA) to starch by ceric ion. The variables affecting the grafting of AN and AA were investigated with granular wheat starch dispersed in aqueous N,N-dimethylformamide and ceric ammonium nitrate as catalyst. Results showed that the concentrations of monomer and catalyst are the major factors influencing the grafting of AN; thus the monomer content of the grafts can be regulated by these variables. The grafting of AA is also influenced by these variables, but to a much less degree. Increasing concentrations of monomer promote homopolymerization and increasing concentration of catalyst inhibit grafting. The extent of grafting of this monomer can best be controlled by reaction time. Under the most favorable conditions, maximum grafting efficiency (ratio of amount of grafted monomer to total amount of monomer converted to polymer) was 87% for AN and 43.8% for AA. Although the monomer content of the AN grafts was higher than that of AA grafts prepared under identical conditions, the number of branches in the grafts was almost the same; only the length of the branches was different. The AN-starch grafts have branches of higher molecular weight.     

Preirradiation grafting of acrylonitrile onto polypropylene monofilament for biomedical applications: I. Influence of synthesis conditions

Graft polymerization of acrylonitrile onto polypropylene (PP) monofilament was carried out by a preirradiation method using a ⁶⁰Co gamma radiation source. The influence of synthesis conditions, such as preirradiation dose, reaction time, monomer concentration, reaction temperature and additives was determined. The grafting was considerably influenced by the instantaneous swelling of the monofilament in the reaction mixture during the course of the grafting process. The order of dependence of the rate of grafting on monomer concentration was found to be 1.04. The nature of the medium of the grafting and the additives had profound influence over the grafting reaction. The accelerative effects of solvent medium on the grafting were higher in methylethyl ketone (MEK) and dimethylformamide (DMF) as compared to methanol. At the same time, partial replacement of DMF with water led to acceleration in the grafting with peak maxima at 20% solvent composition. The addition of a small amount of sulfuric acid to the reaction mixture also resulted in a significant acceleration of the degree of grafting.     

Grafting onto wool. I. Ceric ion-initiated grafting of poly(methyl acrylate) onto wool

Poly(methyl acrylate) has been grafted onto wool by using ceric ion as redox initiator in an aqueous medium. Initiation by ceric ammonium nitrate (CAN) was carried out in the presence of nitric acid of varying concentration at 35, 45, and 50°C for a period of 1.5 or 3 hr. Percent grafting was found to be dependent on concentrations of acid and monomer, reaction time, and temperature. Above 45°C, a considerable amount of homopolymer was formed; at 35°C, very little grafting of poly(methyl acrylate) was observed. Nitric acid catalyzed the reaction and a concentration of 0.17–0.19M HNO₃ was found suitable.     

Physical properties of some low polymer content radiation-grafted wool copolymers

Wool copolymers with low polymer content (6–18%) have been prepared by radiation grafting techniques. Supercontraction, density, and formic acid vapor sorption measurements have been used to assess changes in the keratin structure produced by the grafting processes. Kinetic studies of the contractile forces developed in the first (reversible) stage of the supercontraction of wool in lithium bromide showed that grafting with poly(N-methylol acrylamide) or polyacrylonitrile has a “repairing” action which offsets changes in the wool structure produced by the small radiation dose (2 Mrad) used for the grafting process. By contrast, grafting with poly(vinyl acetate) had no repairing effect. The bonds formed by grafting of poly(N-methylol acrylamide) or polyacrylonitrile to keratin do not reduce swelling of the wool by formic acid, which is a measure of effective crosslink density. Grafting with poly(vinyl acetate) led to increased swelling by formic acid, indicating some disruption of the keratin structure during polymerization. It is suggested that the role of the grafted polymer is mainly to stabilize the hydrogen-bonded secondary network by interaction between the polypeptide and polymer chains.     

Graft polymerization of acrylic monomers onto starch fractions. I. Effect of reaction time on grafting methyl methacrylate onto amylose

A study was made of the ceric-ammonium-nitrate-initiated graft polymerization of methyl methacrylate (MMA) onto a lineal fraction of starch (amylose). Grafting yields were determined by extraction with appropriate solvents: 1,2-dichloroethane for homo-PMM, and 0.5N NaOH for ungrafted amylose. Percent grafting was calculated by acid hydrolysis with 1N HCl. Molecular weights of PMMA side chains were determined by gel permeation-chromatography. Grafting efficiencies ranged from 72 to 83%, grafting, from 190 to 271%, and frequency of attachment of side chains, from 900–1250 glucose units per chain. The results observed are discussed.     

Water sorption and diffusion coefficients of protons and water in PVDF-g-PSSA polymer electrolyte membranes

Water sorption properties, proton NMR spectra, and diffusion of water and protons in poly(vinylidene fluoride)-graft-polystyrene sulfonic acid (PVDF-g-PSSA) polymer electrolyte membranes were studied. Sorption curves for the membranes with different degrees of grafting in protonated and Na⁺ form were measured by equilibrating the membranes over saturated salt solutions. The membrane water content was found to be sensitive to changes in relative humidity (RH). The water/sulfonic acid ratio λ for the protonated samples was around 2 at 20% RH and increased to λ ∼ 30 at 100%. Proton NMR, pulsed field gradient proton NMR (PFG-NMR), and impedance measurements were made on membranes with different λ. In the proton NMR spectra only one peak was found, originating from the water in the membrane. The chemical shift of the peak was found to be dependent on the counterion and the water content. The water self-diffusion coefficients D_H2O, measured by PFG-NMR, increased with degree of grafting and water content of the membranes. The proton conductivity and the calculated proton mobility decreased more steeply than the D_H2O with decreasing water content. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2893–2900, 1999     

Radical grafting on lignin. Part I. Radiation-induced grafting of styrene onto hydrochloric acid lignin

By irradiation with gamma rays styrene was grafted onto hydrochloric acid lignin. When the graft polymers were subjected to nitrobenzene oxidation, the vanillin yields indicated two kinds of reaction occurring in the grafting. Polystyrene branches were separated from the graft polymers, and their M?_n were determined osmometrically. At grafting ratios of up to 100 the vanillin yields diminished proportionately with increasing grafting, and the M?_n of the branches, 5000, was unchanged. At grafting ratios of more than 100 the vanillin yields were constant, independent of the ratios, but the M?_n values of the branches increased with grafting. Paper chromatography of the aromatic acids obtained by oxidation of methylated lignin and the graft polymer indicated that isohemipic and metahemipic acids were more abundant in the acid fraction of the graft polymer than in the lignin itself. A qualitative mass analysis of the gaseous products evolving from the irradiated lignin showed the presence of hydrogen molecules only. Gamma-ray radiation brought about no change in the yields of vanillin. It was therefore concluded that radiation grafting on lignin at grafting ratios of less than 100 proceeded through the addition of the styrene polymer radicals to the aromatic nuclei of the lignin and that then branches propagated from the aliphatic part of the lignin, where C? H bond scission had been caused by the irradiation. The grafting sites of lignin would be C-5 and C-6 of the guaiacyl nucleus and, probably the β and γ carbon atoms of the aliphatic side chain of the lignin.     

CHARACTERIZATION OF RADIATION GRAFTING DEGREE OF POLYSTYRENEg-ACRYLIC ACID BY XPS

In this work, characterization of radiation grafting degree of polystyrene-g-acrylic acid by XPS was studied. It is found that along with the main peak C_(1s) there is a photoelectron peak at 289.0 eV that appears to be C_(1s) of-(?)-OH group and shows the presence ofpolyacrylic acid grafted on the polystyrene The grafting degree obtained by XPS is in agreement with that from the gravimetric method.     

Radiation-induced graft copolymerization of mixtures of styrene and acrylamide onto cellulose acetate. I. Effect of solvents

The grafting of styrene and acrylamide, from both their binary and unitary systems, on cellulose acetate film was studied by means of the cobalt-60 postirradiation grafting technique. The extent of grafting was found to be dependent on preirradiation dose, reaction time, and temperature, and the optimum conditions were evaluated. The effect of solvents, e.g., water, methanol, ethanol, isopropanol, and t-butanol were studied. The composition of the binary mixture as well as the nature of the alcohol used as the solvent were found to have a strong influence in modifying the course of grafting. Each component of the binary monomer mixture was found to sensitize the grafting of the other, when the former is present in relatively large concentration. The observed results are discussed in detail in terms of relative molecular reactivity and reactivity ratios.     

Preparation of poly(ε-caprolactone)-co-poly(acrylic acid) by radiation-induced grafting

Acrylic acid was grafted onto poly(ε-caprolactone) (PCL) films by using electron beam (EB) preirradiation technique. The effect of reaction time, monomer concentration, radiation dose, time between irradiation and grafting, radiation atmosphere, and polymer crystallinity on the extent of grafting were studied. Silver and tin ions were attached to the grafted chains in order to study the grafting process. The irradiation in air was initially more rapid, but the final extent of grafting was the same when irradiated in nitrogen atmosphere. Maximum grafting extents exceeding 400% could be obtained. The optimal grafting was obtained at an acrylic acid to water ratio of 30 : 70. The grafting process could be initiated at a dose as low as 12 kGy. The grafting process proved to start at the surface and was extended into the bulk with time. The ability to form crystals was reduced as the grafting extent increased. The water uptake of the poly(ε-caprolactone)-graft-poly(acrylic acid) was increasing with increasing grafting extent, but reached a maximum of ca 100% for all grafting extents above 85%. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1805–1812, 1998     

Spectroscopic study of the penetration depth of grafted polystyrene onto poly(tetrafluoroethylene‐co‐perfluoropropylvinylether) substrates. 1. Effect of grafting conditions

This study concerns the radiation grafting of styrene onto poly(tetrafluoroethylene‐co‐perfluoropropylvinylether) (PFA) substrates and the penetration depth of the graft. Grafting was obtained by the simultaneous irradiation method, and the spectroscopic analysis was made with the micro‐Raman technique. Effects of grafting conditions such as the type of solvent, dose rate, and irradiation dose on the grafting yield were investigated. Of the different solvents used, the most efficient in terms of increasing grafting yield were dichloromethane, benzene, and methanol, respectively. A mixture of methanol and dichloromethane used as a solvent for styrene achieved a higher degree of grafting and concentration of grafted polystyrene onto the surface of PFA substrates than solutions of the monomer in the separate solvents. The degree of grafting increased with increasing radiation dose up to 500 kGy, stabilizing above this dose. However, the grafting yield decreased with an increase in the dose rate. The increase in the overall grafting yield was accompanied by a proportional increase in the penetration depth of the grafts into the substrate. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3191–3199, 2002     

Cationic polymerization of α-methylstyrene from polydienes. I. Synthesis and characterization of poly(butadiene-g-α-methylstyrene) copolymers

The preparation of poly(butadiene-g-α-methylstyrene) copolymers was investigated with three different alkylaluminum coinitiators. The alkylaluminum compounds in conjunction with polybutadiene which contained a low concentration of labile chlorine atoms initiated the polymerization of α-methylstyrene to produce graft copolymers. Trimethylaluminum gave higher grafting efficiencies than diethylaluminum chloride at comparable monomer conversions. Triethylaluminum produced only very low monomer conversions (<5%), even at long reaction times, and for this reason was not studied extensively. The number of grafts per polybutadiene backbone was determined for a number of copolymers and found to increase slightly as the allylic chlorine concentration in the polybutadiene backbone was increased. In all cases, however, only a low percentage of the available labile chlorine sites along the polybutadiene backbone resulted in grafted α-methylstyrene side chains. The addition of small quantities of water to the polymerization solvent greatly enhanced the grafting rate and ultimate monomer conversion during the synthesis of these poly(butadiene-g-α-methylstyrene) copolymers. The mechanistic role of water during these grafting reactions is unknown at the present time.     

Microwave-Assisted Synthesis and Characterization of Poly(itaconic acid) Grafted Gellan Gum

Poly(itaconic acid) was grafted on GG in aqueous medium under microwave irradiation using a catalytic amount of BPO. Grafted copolymers (GG-g-PIA) were characterized by FT-IR, TGA, and SEM techniques. The influence of microwave power, exposure time, and composition of the reaction mixture on extent of grafting was studied. Conditions for obtaining the highest extent of grafting were optimized. The rate of grafting was determined from weight measurements. The overall activation energy for grafting is found to be to be 28.3 kJ/mol, indicating the possibility of occurrence of the grafting process with absorption of low thermal energy.     

Irradiation-grafted polymeric films. I. Preparation and properties of acrylic acid–grafted polyethylene films

Graft copolymers of low-density polyethylene film and acrylic acid have been prepared by the direct grafting technique. The properties of 27.4, 33.9, 41.2, and 46.4 wt-% poly(acrylic acid) graft copolymer films have been compared. Measurements include degree and uniformity of grafting, gel water content, degree of swelling on wetting, tensile strength, elongation, ion-exchange capacity, water-vapor transmission, and water flux and solute rejection under reverse osmosis conditions. These properties were found to vary as the composition of the graft copolymer changed; most properties were found to be a linear function of the degree of grafting.     

Liquid crystal polymers. IX. Copolyesters of trans-4,4′-stilbenedicarboxylic acid, 1,4-butanediol,and aromatic dicarboxylic acids

Copolyesters of trans-4,4-stilbenedicarboxylic acid (SDA), terephthalic acid, and 1,4-butanediol exhibit thermotropic liquid crystallinity if at least 40 mol % SDA is present (acids total 100 mol %); SDA/2,6-naphthalenedicarboxylic acid/1,4-butanediol copolyesters are liquid crystalline if at least 30 mol % SDA is present. The effects of SDA content on the thermal, rheological, plastic, and fiber properties of the copolyesters were determined. The SDA component increases the relaxation times of the polymers and enables injection-molded plastics and melt-spun fibers to have significantly increased tensile strength and stiffness.     

Interference by methyl levulinate in determination of total fat in low-fat, high-sugar products by gas chromatographic fatty acid methyl ester (GC-FAME) analysis.

Gas chromatographic fatty acid methyl ester (GC-FAME) analyses of some acid-hydrolyzed foods revealed a large peak that did not correspond to any FAME standards. The unknown peak eluted just after the C12 FAME. If the fatty acid response factor and the conversion factor for the nearest calibrated peak (C12 FAME) were used to determine the total fat, the resulting total fat determination was much higher than expected. This peak was present only in acid-hydrolyzed samples and was absent in extracts obtained with supercritical CO2 or solvents without acid hydrolysis. The compound was isolated, analyzed by mass spectrometry and nuclear magnetic resonance spectroscopy, and proved by synthesis to be methyl-4-oxopentanoate (methyl levulinate). Its source was determined to be sugar in the product formula. Levulinic acid is produced by acid hydrolysis of sugar and is transesterified by BF3 in methanol to methyl levulinate. Although methyl levulinate may appear in the GC analyses of any acid-hydrolyzed products containing sugar, if the ratio of fat to sugar is high, the impact of methyl levulinate on fat determination would be small. On the other hand, the presence of methyl levulinate in analyses of low-fat, high-sugar products is potentially problematic if not recognized, although GC analysis can account for the presence of this compound.     

Graft Copolymerization of 4-Vinylpyridine Onto Modified Cellulosic Fibers. the Ceric Ion Concentration Effect

The graft copolymerization of 4-vinylpyridine was carried out on mercerized cellulose and partially carboxymethylated cellulose (PCMC) using eerie ammonium nitrate (CAN) as the initiator. the grafting parameters (grafting efficiency (GE), graft yield (G), and total conversion (C¹)) were studied as a function of CAN concentration. It was shown that by increasing the CAN concentration, G and C, reached a maximum. the graft yields for PCMC were significantly higher than those for mercerized cellulose. the largest GE values appeared for PCMC and mercerized cellulose at low and high CAN concentrations, respectively. the Ce(IV) consumption during grafting increased with rising concentration of CAN, and it was greater in the case of PCMC than of mercerized cellulose. After acid hydrolysis of the polysaccharide backbone, the average molecular weight of grafts was determined viscometrically. Molecular weight decreased with initiator concentration. Graft frequency (GF), on the other hand, increased with CAN concentration. GF for PCMC was higher than that for mercerized cellulose. Ce(IV) consumption increased with CAN concentration and it was lower for mercerized cellulose than that consumed during grafting on PCMC. After that, the effect of CAN concentration on the graft copolymerization onto PCMC was examined while the total nitrate ion concentration was maintained constant at 1.59 M by addition of sodium nitrate. Maximum G, C¹ and Ce(IV) consumption were higher than in the previous case.     

Synthesis of polynucleotide analogs by grafting optically active adenine,cytosine, and hypoxanthine derivatives onto polytrimethylenimine

A new family of polynucleotide analogs were prepared by grafting nucleic acid base derivatives onto polytrimethylenimine. Several new optically pure α-nucleic acid base substituted propanoic acids were prepared as pendant groups. The (R)-ethyl adeninylpropanoate was obtained from adenine and (S)-ethyl lactate by utilizing a diethyl azodicarboxylate-triphenyl phosphine method. Subsequent hydrolysis of the ester in aqueous acid gave the (R)-adeninylpropanoic acid without racemization. The reaction of cytosine sodium salt with (S)-ethyl 2-[(methylsulfonyl)oxy] propanoate produced the 20% racemized (R)-ethyl 2-(cytosin-1-yl)propanoate. The optically pure ester was obtained by recrystallization from ethyl alcohol, which was hydrolyzed in aqueous acid to give the (R)-acid with 66% enantiomeric excess. The (R)-2-(hypoxanthin-9-yl)propanoic acid was prepared by reaction of (R)-2-(adenin-9-yl)propanoic acid with sodium nitrite. The pendant groups were allowed to react with N-hydroxy compounds in the presence of dicyclohexylcarbodiimide to give the active esters. These active esters underwent reaction with N,N-dipropylamine to provide monomer model compounds. The pendant groups were grafted onto polytrimethylenimine by using the active ester method. The racemization reactions were observed in the grafting reactions. The resulting polymers showed a range of percent grafting from 60 to 80%.