共查询到20条相似文献,搜索用时 10 毫秒
1.
B. N. Misra P. S. Chandel 《Journal of polymer science. Part A, Polymer chemistry》1977,15(7):1545-1548
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. 相似文献
2.
B. N. Misra P. S. Chandel 《Journal of polymer science. Part A, Polymer chemistry》1980,18(4):1171-1176
Grafting of poly(methyl acrylate) onto wool has been carried out in an aqueous medium at 45 ± 1°C by using ceric ammonium nitrate (CAN) in the presence of triethylamine, diethylamine, n-butylamine, triethanolamine, and N,N-dimethylaniline. The percentage of grafting varied with the nature and concentrations of the amines. Reactivity of the different amines toward grafting reactions followed the order: triethylamine > diethylamine > n-butylamine > triethanolamine ≥ N,N-dimethylaniline. In the presence of N,N-dimethylaniline grafting did not occur. An attempt has been made to explain the observed reactivity of Ce4+ in various amine systems in graft copolymerization reactions. 相似文献
3.
Padma L. Nayak Subasini Lenka Nrusingha C. Pati 《Journal of polymer science. Part A, Polymer chemistry》1979,17(11):3425-3434
The use of hexavalent chromium to initiate graft copolymerization of methyl methacrylate onto wool fibers has been investigated. The rate of grafting was determined by varying monomer, chromium(VI), temperature, acidity of the medium, nature of wool, reaction medium, and redox system. The graft yield increases with increasing monomer concentration up to 0.65M, and, with further increase of monomer the graft yield decreases. The graft yield increases with increasing chromium(VI) concentration. The grafting is considerably influenced by chemical modification of wool prior to grafting. The effect of certain inorganic salt and anionic surfactant on the rate of grafting has been investigated. The graft yield is influenced by thiourea concentration; it decreases with increasing thiourea concentration. 相似文献
4.
Per Mnsson Lars Westfelt 《Journal of polymer science. Part A, Polymer chemistry》1981,19(6):1509-1515
Well-defined low-molecular-weight polystyrene was grafted onto cellulose acetate in a homogeneous solution. The grafting was performed by esterifying the free hydroxyls in the cellulose acetate (acetyl DS 2.5) with anionically prepared polystyrene having a carboxylic acid group at one end of the chain. The carboxylic acid end group of the polystyrene was activated by either conversion to the corresponding acid chloride, or by reaction with trifluoroacetic anhydride. Pyridine and the more active 4-dimethylaminopyridine were used as catalysts in the esterifications. The polystyrene contents of the copolymers varied between 10 and 80% and the molecular weights of the polystyrene grafts were 2500, 12,100 and 17,100 (M?w/M?n = 1.1). 相似文献
5.
Kozo Arai Masamichi Shimizu Machiko Shimada 《Journal of polymer science. Part A, Polymer chemistry》1973,11(12):3271-3281
In order to study the termination reaction of polymer radicals in the viscous media of wool fibers, reduced, methylated, and S-carboxymethylated wool fibers were used for graft copolymerization of methyl methacrylate and styrene. With termination of poly(methyl methacrylate) radicals, two different termination reactions, recombination and disproportionation, were together involved in the grafting systems studied. The occurrences of two termination reactions in the system could be correlated with the mobility of the wool chain controlling the radical end mobility. With decreasing disulfide content in the fibers, disproportionation predominantly takes place among the mobilized chains. At a constant disulfide, the thiol content or the concentration of thiol anions becomes the determining factor for the termination reaction. A possible explanation for these phenomena in terms of the thiol and disulfide interchange reaction is presented. On the grafting of styrene, additional evidence was obtained that prevention and retardation of the interchange reactions followed mechanochemical bond scission of the disulfide and other covalent bonds and produced new free radicals which could initiate chain reactions. 相似文献
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Polystyrene nanoparticles with grafted chains of an amino functionalized polymer were prepared by a two-step polymerization process. In the first step, the polystyrene seed particles were synthesized by the conventional batch emulsion polymerization using terpolymer HAS (hydroperoxide monomer, acrylic acid, and styrene) as a surface-active initiator. The surface of the obtained particles contains carboxyl groups, which are responsible for the latex stability, and residual undecomposed hydroperoxide groups. Therefore, in the second step, an amino functional monomer was grafted onto the hydroperoxide modified polystyrene particles by a "grafting from" approach. X-ray photoelectron spectroscopy, NMR, and scanning electron microscopy were used to examine the surface of the amino functionalized particles. The amount of incorporated amino groups onto the particles was determined by fluorescenometric titration. In general, the number of amino groups on the particle surface increased with the increase of the functional monomer content in the reaction mixture. The incorporation of the functional monomer was also confirmed by electrophoretic measurements. Final particles possess amphoteric character due to the presence of amino and carboxyl groups on the surface. Adsorption of human immunoglobulins G onto the amino functionalized particles was studied as a function of pH and ionic strength. The covalent binding of human IgG was performed using the glutaraldehyde preactivation method. The immunoreactivity of the latex-IgG complex was examined by the latex agglutination test. 相似文献
8.
Graft copolymerization of methyl methacrylate (MMA) onto Himachali wool fiber has been investigated in aqueous medium by using γ irradiation from a 2100 Ci60CO source as means of initiation. Graft copolymerization was carried out by the mutual method in nitrogen atmosphere as well as in air. Effect of mineral acids and acetic acid on percentage of grafting was studied. Percentage of grafting was determined as functions of total dose, concentration of monomer, and concentration of acids. Maximum percentage of grafting in the presence of acids occurred in nitrogen atmosphere at a total dose of 1.05 MR. All the acids were found to influence grafting and the reactivity of different acids towards graft copolymerization was found to follow the order: H2SO4 > HCl > HNO3 > HC1O4 > HOAc. An attempt has been made to explain the reactivity order of different acids in the light of the mechanism proposed for γ-irradiation-induced graft copolymerization of vinyl monomer onto wool fiber. 相似文献
9.
Kozo Arai Masamichi Shimizu Machiko Shimada 《Journal of polymer science. Part A, Polymer chemistry》1973,11(12):3283-3292
The graft copolymerization of methyl methacrylate in S-carboxymethylated wool fibers was investigated in the aqueous LiBr-K2S2O8 system. The rate of grafting, the degree of polymerization of graft polymer, and the number of grafting sites were determined on varying the thiol content at a constant concentration of monomer. Kinetic considerations lead to the following expression in agreement with the experimental results: Z/DP = {(ktd + ktc)/kp2[M]2} Rp, where Z is the number of DNP endgroups of polymer; DP is the average degree of polymerization; kp, ktd, and ktc are the rate constants of propagation, termination by disproportionation, and termination by recombination, respectively; [M] is the concentration of monomer in fibers, and Rp is the overall rate of grafting. For wool fibers in media sufficiently high viscosity, the rate constants ktd and ktc of diffusion-controlled termination are approximately equal and not affected by the change in cross-link density, provided that the thiol and disulfide interchange occurs. The possibility of occurrence of mechanical bond scission through a radical mechanism is involved in systems with extremely small amounts of thiol groups. 相似文献
10.
Polystyrene materials with good solubility in liquid scintillation cocktails are used to wipe off different types of surfaces in order to determine the tritium removable contamination with the help of a liquid scintillation counter. This paper analyses hydrophilic surface modifications by radiation induced grafting of acrylic groups onto extruded polystyrene plates. Two grafting methods were used: (a) exposure of extruded polystyrene plates, immersed in aqueous acrylic acid solution, to a gamma radiation of a Co-60 source, and (b) exposure of extruded polystyrene plates to a Co-60 source, followed by the immersion of extruded polystyrene plates in aqueous acrylic acid solution. The grafting of acrylic was proved by IR spectrometry and by radiometric methods using acrylic acid labelled with tritium. 相似文献
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Chemical patterning of inorganic substrates by soft lithography has enabled various high-tech applications and cutting-edge fundamental research. In this paper, we report on methods for the grafting and patterned grafting of block copolymer nanotubes onto glass and mica surfaces. Under optimized conditions the density of such grafted nanotubes can be high, and most of the grafted tubes are in a standing position even after solvent evaporation. Surfaces modified with exotic reagents such as block copolymer nanofibers or nanotubes may find applications in biosensing, etc. 相似文献
14.
Yagoub Mansoori Khadijeh Roojaei Mohammad RezaZamanloo Gholamhassan Imanzadeh 《高分子科学》2012,30(6):815-823
An account of the experiments on preparing polystyrene(PS) nanocomposites through grafting the polymer onto organophilic montmorillonite is reported.Cloisite 20A was reacted with vinyltrichlorosilane to replace the edge hydroxyl groups of the clay with a vinyl moiety.Because the reaction may liberate HC1,it was performed in the presence of sodium hydrogencarbonate to prevent the exchange of quaternary alkylammonium cations with H~+ ions.Only the silanol groups on the edge of the clay react with vinyltrichlorosilane.The radical polymerization of the product with styrene as a vinyl monomer leads to chemical grafting of PS onto the montmorillonite surface.The homopolymer formed during polymerization was separated from the grafted organoclay by Soxhlet extraction.Chemical grafting of the polymer onto Cloisite 20A was confirmed by infrared spectroscopy.The prepared nanocomposite materials and the grafted nano-particles were studied by XRD.Exfoliated nanocomposites may be obtained for 0.5 wt%-l wt%clay content.The nanocomposites were studied by thermogravimertic analysis(TGA) dynamic thermal analysis(DTA) and dynamic mechanical analysis (DMTA). 相似文献
15.
Methyl methacrylate has been grafted onto wool and silk using the redox system peroxydiphosphate/tartaric acid. The alkali solubility falls with increased grafting. 相似文献
16.
Kozo Arai Michiharu Negishi Tsutomu Suda Kazuko Doi 《Journal of polymer science. Part A, Polymer chemistry》1971,9(7):1879-1891
The stress–strain behavior and hysteresis properties of various grafted wool fibers were studied. Three distinct regions on the stress–strain curve and hysteresis properties characteristic of the native wool fiber remain substantially intact, even though a large amount of a rigid polymer occurs. It was suggested that the microfibril and the matrix nature in the native wool fiber exist in the grafted wool structures. The electron microscopic results were also supported. These results can be explained on the basis of Menefee's model that the longitudinal mechanical behavior is more directly controlled by a high modulus matrix. 相似文献
17.
B. N. Misra P. S. Chandel Ramesh Dogra 《Journal of polymer science. Part A, Polymer chemistry》1978,16(8):1801-1805
In an attempt to modify fibrous protein, poly(vinyl acetate) has been graft copolymerized onto Himachali wool in an aqueous medium by using Fenton's reagent as redox initiator. Graft copolymerizations were carried out at 25, 30, 35, 40, and 45°C for a period of 3 hr. Percentage grafting was found to be dependent upon reaction temperature, concentration of monomers, and the molar ratio of [H2O2]/[Fe+2]. Maximum grafting occurred at 45°C with a molar ratio of [H2O2]/[Fe+2] = 1.43. A small amount of grafting (2.6–2.8%) occurred when grafting was effected at 45°C in the presence of Fe+2 alone. 相似文献
18.
Sachio Yoshikawa Seiichi Machida Norio Tsubokawa 《Journal of polymer science. Part A, Polymer chemistry》1998,36(17):3165-3172
The grafting of polystyrene with controlled molecular weight and narrow molecular weight distribution onto the carbon black surface through the trapping of polymer radicals formed by the thermal dissociation of 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO)-terminated polystyrene (PSt-TEMPO) by the carbon black surface was investigated. PSt-TEMPO was prepared by living radical polymerization of St with the benzoyl peroxide/TEMPO system. When PSt having no terminal TEMPO moiety was heated with carbon black, no grafting of PSt onto the surface was observed. On the contrary, by the heating of PSt-TEMPO with carbon black in m-xylene at 125°C, PSt with controlled molecular weight and narrow molecular weight distribution was grafted onto the surface: the percentage grafting of PSt (Mn = 3.2 × 103;Mw/Mn = 1.07) onto furnace black was determined to be 16.0%. On the basis of the above results, it is concluded that PSt radicals formed by the thermal dissociation of the C ON bond between PSt and TEMPO are trapped by polycondensed aromatic rings of carbon black. The mole number of grafted PSt chains on the carbon black surface decreased with increasing molecular weight of PSt-TEMPO. PSt-grafted carbon black gave a stable colloidal dispersion in THF. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 3165–3172, 1998 相似文献
19.
The influence of graft-copolymerisation reaction between polyester fibres and mixtures of acrylamide (AAm) and acrylic acid (AA) monomers on zeta potential (ζ) of the grafted polymer has been studied. The polyester fibre was rendered amphoteric in nature due to the introduction of the AAm-AA graft mixtures in the substrate. The (?ζ) increased to a considerable extent at higher pH values of the streaming solution due to increased dissociation of -COOH groups of the AA graft component present in the mixture. With the decrease in pH on the acidic side, decrease in (?ζ) was brought about due to suppression of the dissociation of -COOH groups and increase in the protonation of -CONH2 groups. It was observed that (?δζ/ΔpH) ratio serves as a measure of the amphoteric character of the polymer containing mixtures of AAm-AA graft. 相似文献
20.
I. K. Mehta D. S. Sood B. N. Misra 《Journal of polymer science. Part A, Polymer chemistry》1989,27(1):53-62
Acrylonitrile (AN) has been graft copolymerized onto isotactic polypropylene (IPP) by the preirradiation method using Co60 as the source of gamma rays in the presence of ethanol, n-propanol, isopropanol, n-butanol, tert. butyl alcohol, and n-pentanol. Alcohols vary in their ability to influence grafting of AN onto IPP and the following reactivity order was found: n-pentanol > n-butanol > tert.-butanol > n-propanol > ethanol > isopropanol. An attempt has been made to explain the observed reactivity pattern shown by different alcohols. Thermal behavior of the graft copolymer has been compared with that of IPP and irradiated IPP and it was observed that grafted IPP is thermally more stable than IPP and irradiated IPP. 相似文献