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1.
Thomas J. Xue Charles A. Wilkie 《Journal of polymer science. Part A, Polymer chemistry》1997,35(7):1275-1282
It is possible to graft vinyl monomers, such as acrylonitrile, onto polystyrene via anionic processes but not by a radical process. Both homopolymerization of the added acrylonitrile and graft copolymerization in which acrylonitrile units are added to the para position on the benzene ring in styrene occur; the conversion of acrylonitrile into polymer depends upon the time and temperature of the reaction and on the concentration of the anionic initiator, butyllithium. A constant 15–20% of the acrylonitrile is converted to graft copolymer while the remainder is homopolymerized; graft copolymer may be separated from homopolymer by selective precipitation from either N,N′-dimethylformamide or aqueous potassium thiocyanate. Treatment of the mixed graft and homopolymer with aqueous sodium hydroxide converts the nitrile into an acid salt and one may conveniently separate homopolymer from graft copolymer in this way. Each polystyrene chain is grafted with acrylonitrile units. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1275–1282, 1997 相似文献
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Khan F 《Macromolecular bioscience》2005,5(1):78-89
Gamma-radiation-induced graft copolymerization of methyl methacrylate onto natural lignocellulose (jute) fiber was carried out by the preirradiation method in an aqueous medium by using octylphenoxy-polyethoxyethanol as an emulsifier. The different factors that influenced the graft copolymer reaction process were investigated. In the case of radiation-dose-dependent grafting, samples irradiated in the presence of air produced up to 73% graft weight compared to 53% obtained in the case of irradiation in a nitrogen environment. By assuming Arrhenius reaction kinetics, the activation energy (E(a)) of the grafting reaction process was evaluated for different reaction temperatures. Moreover, the graft copolymer reaction was controlled by incorporating a homopolymer-inhibiting agent and three different chain-transfer agents in the reaction medium. The mechanical and thermal properties of jute fiber 'as received' and jute-graft-poly(methyl methacrylate) were also investigated. The results showed that the percentage of grafting with jute fiber has a significant effect on the properties. The kinetic parameters were evaluated from TGA thermograms by using Broido's method in the temperature range 240-350 degrees C. Scanning electron micrographs show that the structural changes on the surface of jute fibers were induced by graft copolymerization of methyl methacrylate monomer. Fiber-fiber surface friction was measured in terms of the average maximum load and the kinetic friction. SEM of jute-graft-poly(methyl methacrylate). 相似文献
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The novel redox system, potassium diperiodatonickelate (Ni(IV))-casein, was used to initiate graft copolymerization of butyl acrylate onto casein under heterogeneous conditions in aqueous 5% potassium hydroxide solution, which showed high grafting efficiency and percent grafting. FT i.r. spectroscopy, thermal analysis and scanning electron microscopy characterized the structures and properties of the grafted copolymer. The effects of synthesis variables in the graft copolymerization have been discussed in the light of grafting efficiency, percent grafting and the rate of polymerization. A possible initiation mechanism is proposed. 相似文献
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壳多糖与丙烯酸丁酯的乳液接枝共聚研究 总被引:10,自引:0,他引:10
以十二烷基苯磺酸钠为乳化剂,过硫酸钾-亚硫酸氢钠为引发剂,研究了壳多糖与丙烯酸丁醋的乳液共聚合,结果表明当[K2S2O8]=[NaHSO3]=2.57×10-3mol·1-1,[BA]=0.68mol.1-1,[Chitosan]=19.2g·l-1,在70℃下反应5小时,共聚反应的接技率和接枝效率均较高.用红外光谱,差热分析,X射线衍射,扫描电镜对接技共聚物进行了表征,此外测试了共聚物胶乳成膜的机械性能,表明用丙烯酸丁酯对壳多糖进行接枝改性,可提高壳多糖的韧性,扩大其应用范围. 相似文献
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催化链转移聚合制备接枝型两亲共聚物及其溶液性质研究 总被引:2,自引:0,他引:2
采用大分子单体法制备接枝型两亲共聚物, 通过表面张力仪、偏光显微镜、旋转流变仪和小角X射线衍射研究了两亲共聚物在水溶液中的聚集行为及其相结构. 首先末端带有可聚合双键的聚甲基丙烯酸叔丁酯大分子单体(PtBMA Macromonomer)通过催化链转移聚合法制备, 所用到的催化链转移剂为二水合双(二氟化硼苯二酮肟)合钴(II) (COPhBF). 然后将所得到的大分子单体与丙烯酸正丁酯(BA)进行自由基共聚得到接枝共聚物PBA-g-PtBMA, PBA-g-PtBMA中PtBMA的侧链部分在酸性条件下定量水解成聚甲基丙烯酸(PMAA)并用NaOH中和得到主链疏水侧链亲水的接枝型两亲共聚物PBA-g-P(MAA-Na+). 用Wilhelmy吊片法研究了不同浓度的两亲共聚物水溶液的表面张力, 发现其行为与小分子表面活性剂不同. 同时用动态光散射法测量了两亲共聚物水溶液中聚集体的粒度, 发现在研究的浓度范围内(0.02~10 g/L)聚集体都存在两个粒度分布峰(约30和300 nm). 浓溶液(w=37.5%)的偏光显微照片呈现层状液晶的特征图案, 而流变研究表明此时体系具有明显的粘弹性, 说明体系形成了层状液晶. 并且用小角度X射线衍射测定了层状液晶的层间距, 约为12.6 nm. 相似文献
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通过自由基聚合, 丙烯酸(AA)与辛基酚聚氧乙烯醚丙烯酸酯活性大单体(C8PhEO10Ac)共聚,合成了以聚丙烯酸为主链、C8PhEO10Ac 为支链的水溶性两亲接枝共聚物(PAA-g-C8PhEO10Ac), 用凝胶渗透色谱(GPC)测定其相对数均分子质量为4.37×104, 用FTIR和1H-NMR表征了共聚物的结构和组成, 共聚物分子中丙烯酸单体与活性大单体的摩尔比为9:1, 每个共聚物分子中平均约有32个C8PhEO10侧链. 用表面张力法、荧光探针法和透射电子显微镜对共聚物在水溶液中的自组装行为进行了初步研究, 结果表明, 共聚物分子在第一临界胶束浓度cmc1)和第二临界胶束浓度(cmc2)时都形成了球型胶束. 与cmc1时相比, cmc2时溶液表面张力进一步降低, 胶束内部极性进一步减小, 而且胶束粒径增大、结构紧密. 氯化钠的加入可使共聚物溶液的表面张力和胶束内部极性降低. 相似文献
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Poly(ethylene terephthalate)‐g‐methacrylamide (PET‐g‐MAAm) copolymer was prepared by graft copolymerization in organic solvent/water mixtures by using azobisizobutyronitrile (AIBN) as an initiator. The highest graft yield was obtained in 20/80 (v/v) acetonitrile/water mixture as 30.0%. The effect of polymerization parameters such as the ratio of solvent/water mixture, concentrations of initiator and monomer, temperature and time on the graft yield was studied. The moisture regain of the PET fiber increased with grafting from 0.42% to 3.01%. Thermogravimetric data showed that the thermal stability of PET fibers decreased with grafting and 85% of total weight of 29.7% grafted fiber was lost at 500°C. On the other hand, fiber density decreased with increasing graft yield. At SEM micrographs, the layers oriented in the direction of fiber length were observed on the surface of PET fiber as a result of grafting. 相似文献
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Zhang Fan Chen Min Hu Sheng Cheng Haiming 《Journal of Radioanalytical and Nuclear Chemistry》2017,314(3):1927-1937
Urea, sodium hydroxide and sodium sulfide were used to treat the cuticle layer of wool before graft copolymerization and amidoximation to enhance the uranium uptaking capacity of amidoximated wool fiber based adsorbent (Wool-g-AOs). The wool-g-AOs were used for recovery of U(VI) from aqueous solutions. The simulated nuclear industry effluent was used for investigating the selectivity and industrial applicability of Wool-g-AOs. The adsorption of uranium(VI) on Wool-g-AOs was pH dependent. The Langmuir model fitted well with the equilibrium data. Kinetic data were fitted well to pseudo second order model.
相似文献10.
This paper deals with graft copolymerization of acrylic acid (AA) onto Xinjiang fine wool.fiber in aqueous medium initiated by gamma rays. Graft copolymerization was carried out by themutual irradiation method in limited air. Percent grafting and percent efficiency have been deter-mined as a function of total dose, dose rate, concentration of monomer, wool weight and reactiontemperature. Graft copolymers are characterized with infrared (IR) spectroscopy, scanning elec-tron microscopy (SEM), and X--ray diffractometer. Properties of the grafts were studied, and compared with the virgin fiber. 相似文献
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Photoinitiated graft copolymerization of acrylamide onto chitosan under heterogeneous conditions and in the absence of a photo initiator was investigated. The effect of irradiation time, the amount of chitosan and monomer concentration on the extent of grafting was examined. The maximum grafting percentage obtained was 294%. The copolymer was characterized using carbon-13 nuclear magnetic resonance (13C-NMR) spectroscopy, X-ray diffraction analysis (XRD), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The system designed allows synthesis of grafted chitosan with free amine groups which are otherwise possible only by chemical protection. The swelling properties of copolymer were followed in aqueous solution. 相似文献
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The effect of the concentration of the initial monomer mixture, the comonomer ratio, and temperature on the kinetic parameters of the process and the characteristics of the resulting copolymers in the homogeneous copolymerization of sodium 2-acrylamido-2-methylpropanesulfonate with sodium acrylate in aqueous solutions at 50–80°C in the presence of potassium persulfate is studied. The initial rate of copolymerization and the molecular mass of copolymers increase with the total initial concentration of the monomer mixture and the content of sodium 2-acrylamido-2-methylpropanesulfonate. As temperature increases, the initial rate of copolymerization increases and the molecular mass of the copolymer diminishes. When copolymerization is performed in 10, 30, and 40% aqueous solutions of the monomers, the resulting copolymers are enriched in sodium acrylate units. The content of sodium 2-acrylamido-2-methylpropane-sulfonate units in the copolymer slightly increases with an increase in the total initial concentration of the monomer mixture. 相似文献
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Liu R De Leonardis P Cellesi F Tirelli N Saunders BR 《Langmuir : the ACS journal of surfaces and colloids》2008,24(14):7099-7106
In this work temperature-triggered association and gel formation within aqueous solutions of a new family of cationic poly( N-isopropyl acrylamide) (PNIPAm) graft copolymers have been investigated. Five copolymers were synthesized using aqueous atom transfer radical polymerization (ATRP) involving a macroinitiator based on quaternarized N, N-dimethylaminoethyl methacrylate units (DMA+). The PDMA+) x - g-(PNIPAmn)y copolymers have x and y values that originate from the macroinitiator; values for n correspond to the PNIPAm arm length. The copolymer solutions exhibited temperature-triggered formation of nanometer-sized aggregates at the cloud point temperature, which was 33-34 degrees C. The aggregates were investigated using variable-temperature turbidity, hydrodynamic diameter, and electrophoretic mobility measurements. The aggregates were clearly evident using SEM and flowerlike or spherical morphologies were observed. Variable-temperature electrophoretic mobility measurements revealed that the zeta potentials of the aggregates increased with DMA+ content. A study of the effect of added NaNO3 showed that electrostatic interactions controlled the size of the aggregates. The concentrated graft copolymer solutions showed temperature-triggered gelation when the copolymer concentrations exceeded 5 wt %, Fluid-to-gel phase diagrams were constructed. It was found that electrostatic interactions also controlled the gelation temperature. A correlation was found between aggregate size and the minimum copolymer concentration needed to form a gel. A mechanism for the temperature-triggered structural changes leading to the formation of aggregates (in dilute solution) or gels (in concentrated solutions) is proposed. 相似文献
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淀粉与丙烯酸甲酯的接枝共聚物作为生物降解塑料的研究 总被引:6,自引:0,他引:6
如何解决废弃塑料制品的再资源化和使用无污染的降解塑料是当今人类急待解决的热点课题.淀粉与丙烯酸甲酯(MA)进行接技共聚以制备塑料发泡产品的研究已有报道[‘-‘1,一般认为塑料中淀粉含量在40%以上的产品,很容易在土壤中被微生物降解掉[‘].这些研究都是在水溶液体系中进行的,本文的目的在于开发高淀粉含量的接校共聚物,为此对比了在3种不同体系(MA-CH3OHA12O三元均相溶液体系,水溶液体系和乳液体系)中得到的接校共聚物的力学性能、形态观察与组成情况,发现单纯追求高接技效率与接枝链MA的高分子量并不一定能得到… 相似文献
18.
Influence of mechanical activation on the graft copolymerization of sugarcane bagasse and acrylic acid 总被引:2,自引:0,他引:2
Zuqiang Huang Xingtang Liang Huayu Hu Li Gao Yongjun Chen Zhangfa Tong 《Polymer Degradation and Stability》2009,94(10):1737-1745
Sugarcane bagasse (SCB) was mechanically activated by home-made high efficiency stirring mill. Graft copolymers (SCB-g-PAA) of SCB with different mechanical activation times (tM) and acrylic acid (AA) have been synthesized by using ammonium persulfate/sodium sulfite redox pair as an initiator in aqueous solution. The effect of tM on the graft co-polymerization was evaluated by grafting ratio (GR) and grafting efficiency (GE). In addition, scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and differential scanning calorimetry (DSC) were used to characterize the granular morphology, functional groups, crystal structure and thermal properties of the product. It was found that the mechanical activation could split fiber bundles and decrease significantly the crystallinity. SCB degraded after the mechanical activation (MA) and its thermal stability declined. Moreover, the graft copolymerization was enhanced obviously by MA processing. And GR and GE increased with the increase of activation time. 相似文献
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Two copolymers containing p-tolylcarbamoyl pendant group poly (MAMT-co-VAc) and poly(MAMT-co-MA) were synthesized f and the graft copolymerization of AAM onto these two func-tional copolymers films initiated with ceric salt were carried out in aqueous solution for variousperiods at 30℃. The formation of graft copolymer was verified by water absorption, ESCA andSEM photographs. Based on the results of the study of the initiation mechanism of model com-pounds and ceric salt systems, the reaction mechanism of the graft copolymerization initiated withceric salt was proposed. 相似文献
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B. N. Misra J. Kishore M. Kanthwal I. K. Mehta 《Journal of polymer science. Part A, Polymer chemistry》1986,24(9):2209-2215
In an attempt to modify water-soluble synthetic polymers, graft Copolymerization of methylmethacrylate (MMA) and ethyl acrylate (EA) onto poly(vinyl alcohol), PVA, has been studied by using gamma irradiation from a Co60 source as initiator. The graft copolymerization was carried out in an aqueous medium by the mutual method in air. The effect of total dose and concentration of vinyl monomers on percentage of grafting has been determined. Water plays a significant role in the enhancement of graft copolymerization and the optimum amount of water to afford maximum grafting has been evaluated. The effect of CH3OH on aqueous grafting of MMA and EA by radiation method has been studied. The graft copolymer has been characterized by IR spectroscopic and thermogravimetric methods. 相似文献