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1.
John D. Van Dyke Kim L. Kasperski 《Journal of polymer science. Part A, Polymer chemistry》1993,31(7):1807-1823
Dried samples of polyacrylamide in an He atmosphere have been subjected to thermogravimetric analysis in the 30–600°C range, and the evolved gases were monitored by FTIR. Water, ammonia, and small quantities of carbon dioxide are released in the first stages of decomposition (220–340°C), where the polymer chains remain intact and the reaction occurs on the pendant amide groups. In the second stage of decomposition (340–440°C), the majority of the weight loss occurs, and main chain breakdown occurs, releasing carbon dioxide, water, nitrile compounds, and imides. Trapping of the gases in this stage and analysis by GC–FTIR and GC–MS reveals the presence of more than 20 decomposition products, and confirms that a large proportion of these can be assigned to glutarimide and its substituted analogs. Imidization and dehydration reactions on the amide groups, as well as free radical breakdown of the main chains, with inter- and intramolecular hydrogen transfer, can account for many of the products of the decomposition. © 1993 John Wiley & Sons, Inc. 相似文献
2.
W.E. Falconer G.R. Jones W.A. Sunder M.J. Vasile Annabel A. Muenter T.R. Dyke W. Klemperer 《Journal of fluorine chemistry》1974,4(2):213-234
Most known non-radioactive pentafluorides have been examined by molecular-beam mass spectrometry and by the deflection of molecular beams in inhomogeneous electric fields. Extensive association of the vapors occurs for all but the lighter pentafluorides and the interhalogens. The interhalogen pentafluorides are strongly polar, consistent with the accepted C4v symmetry. The transition-metal and Group V pentafluorides are all non-polar, except VF5 and CrF5 for which temperature-dependent polarity is observed. However, uncertainty exists as to whether these observations are applicable to monomeric pentafluorides in all cases. Mass-spectral cracking patterns are presented for all species. 相似文献
3.
The Sm+O chemiionization reaction has been investigated theoretically using a method that allows for correlation and relativistic effects. Potential energy curves have been calculated for several electronic states of SmO and SmO+. Comparison with available spectroscopic and thermodynamic values for these species is reported and a mechanism for the chemiionization reaction Sm+O is proposed. The importance of spin-orbit coupling in the excited states of SmO, in allowing this chemiionization reaction to take place, has been revealed by these calculations. This paper shows the metal-plus-oxidant chemiionization reaction. 相似文献
4.
Although 7-methoxy- and 6,7-dimethoxy-2-methyl-4-vinyl-isocarbostyrils could not be isolated and characterised, they have been generated in situ and shown to undergo cyclo-addition reactions with typical dienophiles. The enol acetate of 2-methyl-4-acetylisocarbostyril has also been trapped as its adduct with maleic anhydride and with p-benzoquinone. 相似文献
5.
de Farias RF de Souza JM de Melo JV Airoldi C 《Journal of colloid and interface science》1999,212(1):123-129
The effects exhibited by adsorbed conducting polyaniline on the redox process on a molybdenum oxide surface were studied. Thermogravimetric results indicate a 4% polyaniline deposition. Cyclic voltammograms of the adsorbed polymer on MoO3 show that polyaniline exerts remarkable effects on the molybdenum blue oxidation-reduction process, with oxidation and reduction potentials of 0.33 and 0.18 V, respectively. This effect strongly enhances the electrode response, and can be used as an important tool in qualitative and/or quantitative determinations of molybdenum in solution as well as in any substrate. Copyright 1999 Academic Press. 相似文献
6.
The rearrangement of 2-methyl-1,2-dihydropapaverine (1a) to the corresponding 2-methyl-3-benzyl-3,4-dihydroisoquinolinium ion (3a) has been shown to be a second order rate process with an unusually high entropy of activation. These data, together with an analysis of the orbital symmetry requirements, have been shown to be consistent with the previously proposed double exchange mechanism for this reaction. 相似文献
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9.
Vara Prasad JV 《Organic letters》2000,2(8):1069-1072
[formula: see text] A simple synthesis of heterocyclic thiosulfonates containing indole, indoline, benzoimidazole, and quinoxaline rings is described. The synthesis of these thiosulfonates involves the preparation of the appropriately substituted thiols followed by sulfonylation to give thiosulfonates. The corresponding thiols were prepared in a simple and efficient manner by using a thiocyanation reaction either prior to heterocycle ring formation or after heterocycle ring formation. These thiosulfonates were coupled successfully to the 5,6-dihydropyran-2-one ring to give products that showed excellent HIV protease activity. 相似文献
10.
Bronstein LM Shtykova EV Malyutin A Dyke JC Gunn E Gao X Stein B Konarev PV Dragnea B Svergun DI 《The journal of physical chemistry. C, Nanomaterials and interfaces》2010,114(50):21900-21907
Iron oxide nanoparticles (NPs) with a diameter 21.6 nm were coated with poly(maleic acid-alt-1-octadecene) (PMAcOD) modified with grafted 5,000 Da poly(ethyelene glycol) (PEG) or short ethylene glycol (EG) tails. The coating procedure utilizes hydrophobic interactions of octadecene and oleic acid tails, while the hydrolysis of maleic anhydride moieties as well as the presence of hydrophilic PEG (EG) tails allows the NP hydrophilicity. The success of the NP coating was found to be independent of the degree of grafting which was varied between 20 and 80% of the -MacOD-units, but depended on the length of the grafted tail. The NP coating and hydrophilization did not occur when the modified copolymer contained 750 Da PEG tails independently of the grafting degree. To explain this phenomenon the micellization of the modified PMAcOD copolymers in water was analyzed by small angle x-ray scattering (SAXS). The PMAcOD molecules with the grafted 750 Da PEG tails form compact non-interacting disk-like micelles, whose stability apparently allows for no interactions with the NP hydrophobic shells. The PMAcOD containing the 5,000 Da PEG and EG tails form much larger aggregates capable of an efficient coating of the NPs. The coated NPs were characterized using transmission electron microscopy, dynamic light scattering, ζ-potential measurements, and thermal gravimetry analysis. The latter method demonstrated that the presence of long PEG tails in modified PMAcOD allows the attachment of fewer macromolecules (by a factor of ~20) compared to the case of non-modified or EG modified PMAcOD, emphasizing the importance of PEG tails in NP hydrophilization. The NPs coated with PMAcOD modified with 60% (towards all -MAcOD- units) of the 5,000 PEG tails bear a significant negative charge and display good stability in buffers. Such NPs can be useful as magnetic cores for virus-like particle formation. 相似文献