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91.
Sadiqali Cheruthazhekatt Harald Pasch 《Analytical and bioanalytical chemistry》2013,405(26):8607-8614
High-temperature solvent gradient interaction chromatography (HT-SGIC) is a fast and efficient fractionation technique for the chemical composition analysis of olefin copolymers. The separation of ethylene–propylene random copolymers (EPRs) was achieved on a graphitic stationary phase, Hypercarb, at 160 °C by using linear solvent gradient elution from 1-decanol to 1,2,4-trichlorobenzene (TCB). In the present work, the solvent gradient profile was modified to improve the chromatographic separation of EPRs. With the aim to obtain a better resolution in separation, a slow increase in the volume fraction of TCB was applied. This allowed for a relatively large retention region for linear polyethylene (PE) chains on the column; thereby, a broader elution volume zone between the start of the gradient and the PE elution was achieved. The efficiency of this new gradient profile was demonstrated by analysing two fully amorphous EPR samples. Clear differences in the chemical composition of these EPR samples with similar ethylene contents have been proven by using this modified solvent gradient. The comprehensive chemical composition and microstructure analysis of the SGIC-separated fractions by FTIR revealed that ethylene/propylene (EP) copolymer chains were eluted according to their ethylene/propylene contents and E or P sequence lengths, even though they are distributed in a random manner. These results showed that the solvent composition is an important factor to affect the interactive adsorption or desorption behaviour of EP chains on Hypercarb. In this way, for the first time, the determination of the complex composition and chain structure of EPR samples was achieved within short analysis time, which is not possible till now using other fractionation techniques reported. Figure
A slightly modified solvent gradient method for high-temperature solvent gradient interaction chromatography (HT-SGIC) enabled the fractionation of completely amorphous ethylene–propylene rubbers (EPR) according to their microstructure with high resolution in separation. Presence of EP copolymers having short E or P blocks was identified by combing the HT-SGIC fractionation with FTIR analysis. 相似文献
92.
Andreas Mautner Xiaohua Qin Harald Wutzel Samuel C. Ligon Barbara Kapeller Doris Moser Guenter Russmueller Juergen Stampfl Robert Liska 《Journal of polymer science. Part A, Polymer chemistry》2013,51(1):203-212
Monomers for radical photopolymerization based on vinyl esters (VEs) have recently been identified as suitable alternatives to (meth)acrylates on account of their low irritancy and cytotoxicity. The drawback of most VEs with abstractable hydrogens is their relatively low reactivity compared with (meth)acrylates. Within this article, we proved by photo‐differential scanning calorimetry measurements and real‐time Fourier transform infrared spectroscopy that the thiol‐ene concept is able to improve the photoreactivity of these VEs to a large extent to a level between those of acrylates and methacrylates. Other VEs have now a reactivity of at least the level of similar acrylates. Mechanical properties as determined by Dynamic Mechanical Analysis and Charpy impact tests showed significant toughening of these materials. Furthermore, we were able to confirm low toxicity of all components by osteoblast cell culture experiments. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013 相似文献
93.
Chetan R. Singh Gaurav Gupta Ruth Lohwasser Sebastian Engmann Jens Balko Mukundan Thelakkat Thomas Thurn‐Albrecht Harald Hoppe 《Journal of Polymer Science.Polymer Physics》2013,51(12):943-951
A series of well‐defined poly(3‐hexylthiophene)s (P3HT) of different molecular weight (MW) and high regioregularity was investigated for charge transport properties in as‐cast and melt‐crystallized films. The semicrystalline structure of the P3HT was characterized by X‐ray scattering and Atomic force microscopy. Crystallization by cooling from the melt led to a substantial increase in crystallinity and a stronger alignment of the crystals in comparison to as‐cast films. The increase in crystallinity went along with an increase in hole mobility of up to an order of magnitude as measured by the space charge limited current method. Additionally, the hole mobility depended on the long period of P3HT lamellae and consequently on the MW. In compliance with the long period, the charge carrier mobility first increased with the MW before decreasing again at the onset of chain folding. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013 , 51, 943–951 相似文献
94.
Elvira Welzig Harald Pichler Rudolf Krska Dietmar Knopp Reinhard Niessner 《International journal of environmental analytical chemistry》2013,93(3-4):279-288
Abstract The development of an indirect competitive enzyme immunoassay for the sulfonylurea herbicide metsulfuron-methyl (MSM) is described. In contrast to traditional antibody generation in mammals, this extremely sensitive method is based on chicken egg yolk antibodies (IgY). They were raised in laying hens using an MSM-derivative-BSA hapten as immunogen. With a 1:10000 dilution of the antibody solution and a coating antigen (MSM-derivative-KLH) concentration of 10 μg L?1 the IC50 value achieved for the target analyte was 0.4 μg L?1. The least detectable dose was established at 13 ng L?1. Cross-reactivity was tested with 5 structurally related compounds, where only sulfometuron showed a significant binding. The ELISA was tested with spiked tap and surface water samples. This paper, for the first time, demonstrates the production of high-affinity IgY antibodies for a herbicide compound. 相似文献
95.
The reaction of linear (Si(n)Cl(2)(n)(+2); n = 3-5) and cyclic (Si(5)Cl(10)) perchloropolysilanes with 1 or 2 equiv of LiN(SiMe(3))(2) results in the formation of the bis(trimethylsilyl)amino derivatives (Me(3)Si)(2)NSi(3)Cl(7) (1), (Me(3)Si)(2)NSi(4)Cl(9) (2), (Me(3)Si)(2)N(SiCl(2))(n)N(SiMe(3))(2) (n = 3, 4; n = 4, 5; n = 5, 6), cyclo-(Me(3)Si)(2)NSi(5)Cl(9) (7), and cyclo-[(Me(3)Si)(2)N](2)Si(5)Cl(8) (8). 1-8 easily can be hydrogenated with LiAlH(4) to give the corresponding amino and diamino polysilanyl hydrides. The monosubstituted and cyclic compounds 1, 2, 7, and 8 additionally afford Si-Si bond scission products, which cannot be separated in all cases. Chloro- and dichloro derivatives of Si(3)H(8), n-Si(4)H(10), and n-Si(5)H(12) are obtained from the corresponding aminosilanes and dry HCl. All compounds were characterized by standard spectroscopic techniques. For Si-H derivatives the coupled (29)Si NMR spectra were analyzed to obtain an unequivocal structural proof. 相似文献
96.
The microwave spectrum of 1-thia-closo-dodecaborane(11), 1-SB(11)H(11), has been investigated in the 23-62 GHz spectral region. The molecule is found to have C(5v) symmetry. The spectra of several isotopomers have been assigned and a precise substitution structure of the non-hydrogen atoms has been determined. The structure is in quite good agreement with the one determined previously by electron diffraction. Density functional theory calculations at the B3LYP/cc-pVTZ level were found to predict a structure that is in good agreement with the substitution structure. 相似文献
97.
Joeng-Shein Chen Harald Berndt Günther T?lg 《Fresenius' Journal of Analytical Chemistry》1992,344(12):526-534
Summary Various possibilities for the determination of trace impurities in high-purity iron by atomic spectrometry were investigated in detail. For Ba, Bi, Cd, Co, Cr, Cu, Mn, Ni, Pb, Ti and V, flame AAS, furnace AAS and ICP-OES were firstly evaluated in terms of their power of detection. Detection limits in the g/g-range could be achieved by direct determination. For determination in the ng/g-range a removal of iron by a solvent extraction technique prior to the instrumental measurement was required. The power of detection of direct determination, and of combined procedures were compared with regard to routine applicability and a minimization of systematic errors. 相似文献
98.
99.
100.
Oxidefluorides of Niobium and Tantalum The reaction of NbF5 with SiO2 (silica glass ampules) at 310°C or with SiO2 (Aerosil) at 180°C always leads to NbO2F. To the contrary the reaction with laboratory glass (Jenaer Geräteglas) at 130°C leads to NbOF3. TaF5 reacts in silica glass ampules at 400°C by formation of TaO2F, however at 300°C or 260°C by formation of TaOF3. Silica glass did not react with NbF5 at 130°C, however Nb2O5 and NbF5 gave at 130°C in silica glass ampoules NbOF3. Similarly, TaF5 and Ta2O5 or TaO2F formed at 260°C in nickel ampoules TaOF3. The chemical and the thermochemical behaviour of oxidefluorides have been investigated. The compounds NbOF3 and TaOF3 are isomorphic. Lattice constants are mentioned. 相似文献