Fenton's reagent-initiated graft copolymerization of acrylonitrile onto sodium alginate

Graft copolymerization of acrylonitrile (AN) onto sodium alginate was studied in an aqueous medium using ferrous ammonium sulfate–hydrogen peroxide (Fenton's reagent) as the redox initiator. To optimize the reaction conditions for affording maximum percentage of grafting, the concentrations of sulfuric acid, initiator components, monomer, and also temperature and time were varied. The results are discussed and a reaction mechanism is proposed. © 1994 John Wiley & Sons, Inc.     

Production of bioethanol by immobilized Saccharomyces Cerevisiae onto modified sodium alginate gel

BACKGROUND: Microbial bioethanol production is an important option in view of the finite global oil reserves. Bioethanol fermentation was carried out using immobilized microorganisms (Saccharomyces cerevisiae, Zymomonas mobilis, Pichia stipitis, etc.), which has many advantages compared with the use of free cells. Various support materials have been used for bioethanol fermentation, and alginate gels have been one of the most widely used matrices for cell entrapment. The aim of this study was increased bioethanol production by Saccharomyces cerevisiae immobilized on alginate gels. First, N‐vinyl‐2‐pyrrolidone was grafted onto sodium alginate. Then, the properties of ethanol production were investigated using the matrix obtained. RESULTS: The performance of ethanol fermentation was affected by calcium chloride concentration, N‐vinyl‐2‐pyrrolidone grafted onto the sodium alginate, sugar concentration and the percentage of immobilized cell beads. These effects were optimized to give maximum ethanol production. Ethanol production was accelerated when sodium alginate polymer was modified with N‐vinyl‐2‐pyrrolidone. The maximum concentration, productivity and yield of ethanol were 69.68 g L^?1, 8.71 g L^?1 h^?1 and 0.697 g g^?1, respectively. CONCLUSION: The new polymeric matrix, when compared with sodium alginate, showed better ethanol production due to the hydrophilic property of N‐vinyl‐2‐pyrrolidone. The results suggest that the proposed method for immobilization of Saccharomyces cerevisiae has potential in industrial applications of the ethanol production process. Copyright © 2011 Society of Chemical Industry     

Kinetics and reaction mechanism of fenton's-reagent-initiated graft copolymerization of acrylonitrile onto sodium alginate

The kinetics and mechanism of grafting of acrylonitrile (AN) onto sodium alginate (SA) using Fenton's reagent (Fe²⁺–H₂O₂) has been studied. The experimental results are found to be in good agreement with the proposed kinetic scheme. © 1994 John Wiley & Sons, Inc.     

海藻酸钠负载聚乙烯亚胺功能球对Cu~(2+)吸附研究

以海藻酸钠-聚乙烯亚胺均相水溶胶为前驱体,用溶胶-凝胶法制备了毫米级(2.8³ mm)海藻酸钠负载聚乙烯亚胺(SA-PEI)功能球,考察了pH、吸附时间、初始浓度、温度对Cu3 mm)海藻酸钠负载聚乙烯亚胺(SA-PEI)功能球,考察了pH、吸附时间、初始浓度、温度对Cu⁽²⁺⁾吸附过程的影响。结果表明,SA-PEI功能球对Cu(2+)吸附过程的影响。结果表明,SA-PEI功能球对Cu⁽²⁺⁾最佳吸附pH为5.5,吸附平衡时间为36 h,吸附Cu(2+)最佳吸附pH为5.5,吸附平衡时间为36 h,吸附Cu⁽²⁺⁾为自发、吸热、熵增过程;吸附动力学过程遵循拟二级动力学模型,吸附符合Freundlich等温模型,且在实验浓度范围内,功能球对Cu(2+)为自发、吸热、熵增过程;吸附动力学过程遵循拟二级动力学模型,吸附符合Freundlich等温模型,且在实验浓度范围内,功能球对Cu⁽²⁺⁾最大吸附量为260.5 mg/g;吸附饱和的SA-PEI功能球可以用EDTA-2Na溶液很好的脱附,6次吸附-脱附后仍保持较好的吸附活性。     

海藻酸钠改性铝污泥功能球吸附Cu(Ⅱ)的研究

以铝污泥(AlS)和海藻酸钠(SA)为主要原材料,经过溶胶-凝胶法制备海藻酸钠改性铝污泥(SA-AlS)功能球,研究了温度、pH、初始浓度、吸附时间对Cu(Ⅱ)吸附过程所产生的影响。结果表明,SA-AlS功能球在Cu(Ⅱ)的吸附过程中最佳pH为5.5,吸附平衡时间为24 h,吸附过程为自发、吸热、熵增的过程,吸附等温线拟合结果表明,SA-AlS功能球对Cu(Ⅱ)的吸附行为更符合Langmuir模型,表明该吸附过程主要涉及单层吸附;拟一级和拟二级动力学模型研究表明,该吸附过程与拟二级动力学模型更符合,故SA-AlS功能球对Cu(Ⅱ)的吸附过程主要由化学吸附控制。吸附饱和的SA-AlS功能球可以用EDTA-2Na溶液很好地脱附,5次吸附-脱附后仍保持较好的吸附活性。     

Graft copolymerization of itaconic acid onto sodium alginate using ceric ammonium nitrate as initiator

Graft copolymers of sodium alginate (NaAlg) with itaconic acid (IA) were prepared in aqueous solution using ceric ammonium nitrate (CAN) as the redox initiator under N₂ atmosphere. The carboxylic acid groups of IA were neutralized with sodium hydroxide before grafting process. Grafted copolymers as sodium salts (NaAlg‐g‐PIA) were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, intrinsic viscosity measurement, differential scanning calorimetry, and thermogravimetric analysis. The graft yield (GY %) of the graft copolymer and the grafting efficiency (GE %) of the reaction were evaluated comparatively. The effects of the reaction variables such as the reaction time, temperature, percentage of NaAlg, monomer and initiator concentrations on these parameters were studied. It was observed that GY% and GE% increased and then decreased with increasing concentrations of IA and polymerization temperature. The optimum grafting conditions for maximum GY were obtained with a reaction time of 5 h, reaction temperature of 30°C, IA concentration of 0.23 M, CAN concentration of 9.12 × 10^?2 M and percentage of NaAlg 0.5 g/dL. The overall activation energy for the grafting was also calculated to be 1135 cal/mol. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Grafting of methyl methacrylate onto sodium alginate initiated by potassium ditelluratoargentate(III)

Sodium alginate (SA) was graft‐copolymerized with methyl methacrylate in an alkali aqueous solution with potassium ditelluratoargentate(III) (DTA) as the initiator. Graft copolymers with both a high grafting efficiency (>90%) and a high percentage of grafting were obtained, which indicated that the DTA–SA redox pair was an efficient initiator for this grafting. The grafting parameters, including total conversion, grafting efficiency, and percentage grafting, were evaluated comparatively. The dependence of these parameters on temperature and time, monomer concentration, initiator concentration, and SA backbone concentration was also investigated. The overall activation energy of this grafting was calculated as 37.50 kJ/mol. Proof of grafting was obtained from gravimetric analysis and IR spectra. A tentative mechanism involving a two‐step, single‐electron‐transfer process of DTA is proposed to explain the generation of radicals and the initiation of grafting. Some basic properties of the grafted copolymer were studied by instrumental analyses, including thermogravimetry, X‐ray diffraction, and scanning electron microscopy. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1688–1694, 2005     

Controlled release of insecticide carbaryl from sodium alginate,sodium alginate/gelatin,and sodium alginate/sodium carboxymethyl cellulose blend beads crosslinked with glutaraldehyde

Interpenetrating network polymeric beads of sodium alginate (NaAlg) and its blend with gelatin (gels) or sodium carboxymethyl cellulose (NaCMC) have been prepared by crosslinking with a common crosslinking agent, glutaraldehyde (GA), for the release of insecticide carbaryl (Carb). The prepared beads were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. Scanning electron microscopy confirmed the spherical nature and surface morphology of the particles. Bead characteristics, such as carbaryl entrapment efficiency, particle size, equilibrium swelling degree, and carbaryl release kinetics, were determined. The effects of the preparation conditions, such as Carb/NaAlg ratio, time of exposure to GA, blend ratio, and temperature of release medium on the carbaryl release, were investigated for 25 days at 25°C. It was observed that the carbaryl release decreased with increase in crosslinking of network, while it increased with increase in Carb/NaAlg ratio and temperature. The release of carbaryl also increased with increase in Gel or NaCMC content in the blend beads. The highest carbaryl release was found to be 100%, for the beads that were prepared with 1 : 1 NaAlg/Gel at 16 days. The diffusion coefficients have been calculated for the transport of insecticide through the polymeric beads, using initial time approximation method. These values were also consistent with the carbaryl release data. The carbaryl release from most of the bead formulations followed the Fickian trend. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1310–1319, 2006     

多单体固相接枝聚丙烯

用乙醚作分散剂,将接枝单体和引发剂均匀分布到聚丙烯(PP)粒子表面,改善相间传质;以偶氮二异丁腈为引发剂,用固相接枝方法制备了丙烯酸丁酯(BA)-马来酸酐(MAH)-苯乙烯(St)接枝PP。考察了接枝单体用量、引发剂用量、反应温度及时间、界面剂用量等对接枝的影响,用傅里叶变换红外光谱仪、热重分析仪和扫描电子显微镜等对接枝产物进行了表征。结果表明:使用分散剂消除了普通固相反应出现的结块现象,接枝单体分布比较均匀;PP为20.0 g时,n(BA)/n(MAH)/n(St)为2:1:1,接枝单体质量分数为6%,引发剂质量分数为0.3%,在80℃反应1.5 h,得到了接枝率为3.48%的接枝产物;产物的拉伸强度没有变化,但极性和热稳定性得到提高。     

高强度海藻酸盐纤维的制备

采用湿法纺丝方法制备高强度海藻酸盐纤维,研究了影响纤维断裂强度的因素。结果表明:海藻酸钠的β-D-甘露糖醛酸单元(M)/α-L-古罗糖醛酸单元(G)质量比越高,纤维断裂强度越低。采用M/G值为0.32的海藻酸钠为原料,氯化钙水溶液为凝固液,纺丝液质量分数为5.0%,凝固浴质量分数为4.5%,凝固浴温度为40℃,纤维烘干温度为30℃,可制得断裂强度达4.675 cN/dtex的高强度海藻酸盐纤维。     

炭黑原位改性橡胶的研究近展

从炭黑的结构与性能以及炭黑表面接枝聚合机理出发,讨论了原位接枝技术在炭黑原位改性橡胶中的应用与研究,从而为炭黑原位接枝改性橡胶技术提供新思路和方法。     

Study of electrospinning of sodium alginate,blended solutions of sodium alginate/poly(vinyl alcohol) and sodium alginate/poly(ethylene oxide)

Alginate is an interesting natural biopolymer for many of its merits and good biological properties. This paper investigates the electrospinning of sodium alginate (NaAlg), NaAlg/PVA‐ and NaAlg/PEO‐ blended systems. It was found in this research that although NaAlg can easily be dissolved in water, the aqueous NaAlg solution could not be electrospun into ultrafine nanofibers. To overcome the poor electrospinnability of NaAlg solution, synthetic polymers such as PEO and PVA solutions were blended with NaAlg solution to improve its spinnability. The SEM images of electrospun nanofibers showed that the alginate (2%, w/v)–PVA (8%, w/v) blended system in the volume ratio of 70 : 30 and the alginate (2%, w/v)–PEO (8% w/v) blended system in the volume ratio of 50 : 50 could be electrospun into finest and uniform nanofibers with average diameters of 118.3 nm (diameter distribution, 75.8–204 nm) and 99.1 nm (diameter distribution, 71–122 nm), respectively. Rheological studies showed a strong dependence of spinnability and fiber morphology on solution viscosity and thus on the alginate‐to‐synthetic polymer (PVA or PEO) blend ratios. FTIR studies indicate that there are the hydrogen bonding interactions due to the ether oxygen of PEO (or the hydroxyl groups of PVA) and the hydroxyl groups of NaAlg. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Reactive grafting of glycidyl methacrylate onto polypropylene

This work explored the melt‐phase grafting of glycidyl methacrylate (GMA) onto polypropylene on a closely intermeshing corotating twin‐screw extruder (16‐mm screws, 40 : 1 length/diameter ratio). The modification of the base polypropylene to produce GMA‐grafted polypropylene was achieved via peroxide‐induced hydrogen abstraction from the polypropylene followed by the grafting of the GMA monomer or by the grafting of styrene followed by copolymerization with the GMA. In this study, both the position and order of the reactant addition were investigated as a route to improving graft yields and reducing side reactions (degradation). For the peroxide–GMA system, adding GMA to the melt before the peroxide resulted in significant improvements in the graft levels because of the improved dispersion of GMA in the melt. The addition of a comonomer (styrene) was explored as a second route to improving the graft yield. Although the addition of the comonomer led to a considerable rise in the level of grafted GMA, altering the order of the reactant addition was not found to contribute to an increase in the grafted GMA levels. However, variable levels of grafted styrene were achieved, and this may play an important role in the development of grafted polymers to suit specific needs. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Cerium-initiated grafting of acrylonitrile onto cellulosic materials

Grafting of acrylonitrile onto native cotton, swollen cotton, viscose, ramie, and hydrocellulose was studied with tetravalent cerium as initiator. The effect of temperature on the graft yields is examined. With ceric ammonium nitrate the grafting yields are found to be higher at 20 and 40 than at 60°C. Ceric ammonium sulfate, on the other hand, produces more grafting at 60 than at 20 and 40°C. The consumption of ceric ions is less, whereas the per cent graft yields are higher for the swollen cottons and viscose than for native cotton. Graft yields are shown to be related to substrate accessibility if the grafting reaction is carried out under conditions that suppress homopolymerization. Oxidation of these celluloses with Ce^IV has also been studied. It is found that more Ce^IV is consumed during grafting than during oxidation of cellulose under identical reaction conditions. Excess Ce^IV consumed in the grafting reaction has been shown to be directly related to extent of homopolymerization, which accompanies grafting. Some data on the storage stability of the free-radical activity produced by oxidation of cellulose with Ce^IV are also reported. It is observed that the cerium-oxidized samples can initiate graft poly merization even after 4–5 hr. if stored in nitrogen.     

Electron-beam irradiation-induced grafting of acrylonitrile onto polyethylene

Low- and high-density polyethylene (PE) films were grafted with acrylonitrile (AN) by electron beam prior to irradiation. The distribution of graft chains over the cross section of the sample film was analyzed in terms of the distribution of nitrogen atoms contained in the AN by means of an electron probe microanalyzer (EPMA), and graft sites were studied in relation to the effect of grafting temperature on the percent graft and the oxygen permeability of the sample films. It was found that diffusion of AN into the film was the rate-limiting step in the grafting process, thus restricting the grafting to the surface of the film in the initial grafting stages. However, the grafting shifted to the center of film as the graft process proceeded, until a uniform distribution of graft chains was observed across the entire film thickness. High-density polyethylene (HDPE) was found to display a higher percent graft than did low-density polyethylene (LDPE), and percent graft tended to increase with increasing grafting temperature. On the other hand, film oxygen permeability decreased with increasing percent graft, but this decreasing trend decreased with increasing percent graft. These findings suggest that the grafting is initiated by radicals trapped in the amorphous phase near the crystalline regions and at the surface of crystallites and that graft chains grow toward the amorphous regions. As for the radicals contributing to graft polymerization, it appears that AN permeates deeper near the crystalline surface and that graft chains grow from these sites.     

Solid-phase grafting of glycidyl methacrylate onto polypropylene

Free-radical grafting of glycidyl methacrylate (GMA) onto polypropylene (PP) powder was studied in a batch mixer. The reaction temperature was below the melting point of PP so that PP was modified in the solid phase. The graft yield of GMA obtained under various experimental conditions allowed for a good appreciation of the effects of chemical parameters (the concentration of monomer, initiator, and interfacial agent) and those of processing parameters (reaction time and temperature). Toluene was used as an interfacial agent to etch the surface of PP powder to provide more sites for reaction. Quantitative determination of the graft level was performed by wet chemical methods. The results showed that the solid-phase grafting could take place over a temperature range of 100–140°C in the initiation of benzoyl peroxide (BPO). The ultimate GMA grafting level achieved was higher than that obtained in the melt state with dicumyl peroxide (DCPO) as a radical initiator. The grafting of GMA affected the crystalline morphology of PP and speeded up the crystallization process. The energy of activation and initial decomposition temperature of grafted samples were higher than those of ungrafted PP. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 1905–1912, 1997     

PE膜表面接枝间苯二酚

Low density polyethylene film surface-grafted process. Firstly, acrylic acid was grafted to the surface grafting. Secondly, the carboxylic groups in poly （acrylic resorcinol was prepared by a sequential of low density polyethylene by UV photoacid） chains were transferred to acyl chloride groups by the reaction of carboxylic groups with thionyl chloride. The stability of acyl chloride groups in several solvents （alcohol, water, acetone, aqueous NaOH and in N2 atmosphere） was investigated, and N2 atmosphere and acetone were appropriate media to protect acyl chloride groups from side reaction. Finally, resorcinol monomer reacted with acyl chloride to append to the poly（acrylic acid） chains at room temperature. FT-IR ATR was used to characterize the change of carbonyl groups during each step of the grafting process. Furthermore, by the experimental data of gravimetric analysis the grafted resorcinol monomer on the surface of low density polyethylene film was verified to have undergone condensation with acetone further in the resorcinol/acetone solution at 56℃, which might be a useful feature for synthesizing a thermoplastic/thermosetting composition.     

Tributylborane-initiated grafting of methyl methacrylate onto chitin

The grafting of methyl methacrylate (MMA) onto chitin initiated by tributylborane (TBB) was investigated at ordinary temperature. It was found that water was essential to the grafting. No grafting was observed in the usual organic solvents such as n-hexane, tetrahydrofuran, and cyclohexanone. The total conversion and the percentage and efficiency of grafting increased with increasing chitin content. The extent of homopolymer formation also increased with increasing chitin content. The optimum concentrations of TBB and MMA for the grafting were determined. Activation energies were estimated to be about 22.8 and 27.4 kcal/mole for the grafting and homopolymerization, respectively. On the basis of these results the mechanism of the grafting onto chitin was discussed.     

Light-scattering properties of sodium and magnesium alginate

The weight-average molecular weight of a fraction of magnesium alginate was found by light-scattering to be identical within experimental error to that of the corresponding fraction of sodium alginate. The difference in the charge density of sodium and magnesium alginate had no detectable effect on their measured radii of gyration at ionic strength 0.1, but had a great effect on the second virial coefficient of the solutions. The Orfino-Flory theory was used to calculate expansion factors, α, from the second virial coefficients, assuming that these were composed of two terms, one due to polymer-solvent interaction and one due to electrostatic interactions. A comparison with α-values obtained from viscosity data at different ionic strengths suggested that alginate is soluble in water because of electrostatic stabilisation and not because of a favourable polymer-water interaction.     

海藻酸钠荧光多孔支架的制备

采用乳化剂交联法,以海藻酸钠(SA)为原料,Ca Cl2为物理交联剂,制备了海藻酸钠多孔支架;然后分别以0.2 mol/L Zn(Ac)2、Zn Cl2和Zn(NO3)2为交联剂,在海藻酸钠溶液质量浓度为15 g/L,温度为8℃的条件下,制备了竖直贯通的多孔支架;冷冻干燥后,将支架浸泡在KOH/甲醇/无水乙醇混合溶液中(Zn O量子点原位合成法),制备了荧光竖直定向多孔支架。研究了海藻酸钠的质量浓度(5 g/L、10 g/L、15 g/L)及不同干燥方法(冷冻干燥和乙醇逐级脱水法)对制备海藻酸钠多孔支架的影响;将成纤维细胞与海藻酸钠多孔支架共培养,考察海藻酸钠多孔支架的生物相容性,采用Cy3(Cy–N–羟基琥珀酰亚胺酯)与DAPI(4,6–二脒基–2–苯基吲哚)双荧光染色法观察细胞生长情况及采用MTT(3–(4,5–二甲基噻唑–2)–2,5–二苯基四氢唑溴盐)法定量检测了海藻酸钠多孔支架的细胞毒性;对荧光多孔支架的形貌和荧光性能进行了表征。