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11.
Bisfunctionalized m-phenylene ethynylene imine oligomers were polymerized in the polar solvent acetonitrile, resulting in high-molecular weight poly(m-phenylene ethynylene imine)s. It is hypothesized that this polymerization, which proceeds through the reversible metathesis of imine bonds, is driven by the folding of the long m-phenylene ethynylene imine chains. Upon conducting the polymerization in a series of solvents in which the m-phenylene ethynylene oligomers exhibit different folding stabilities, it was possible to correlate the molecular weight of the resulting poly(m-phenylene ethynylene imine)s with the helical stability of the corresponding oligomers. The polymerization was also demonstrated to be reversible and responsive to solvent and temperature changes. 相似文献
12.
Martin R. Bryce Peter J. Skabara Adrian J. Moore Andrei S. Batsanov Judith A.K. Howard Vanessa J. Hoy 《Tetrahedron》1997,53(52):1002-17794
Reactions of tetrathiafulvalenyllithium (TTF-Li) with a range of aldehydes and ketones have been explored for the first time, to provide an efficient route to mono-functionalised TTF derivatives of general formulae TTF-CH(OH)R (R = alkyl, phenyl, tetrathiafulvalenyl and ferrocenyl) and TTF-CR(OH)R′ (R = alkyl, phenyl, R′ = alkyl, phenyl, tetrathiafulvalenyl, ferrocenyl, and R-R′ = fluorenyl). Subsequent transformations involving the reactive alcohol group of some of these compounds are reported. The structures of the three title compounds have been established by single-crystal X-ray analysis. 相似文献
13.
Sequence-specific phenylacetylene oligomers consisting of functionalized monomers (hexyl benzoate, hexyl phenyl ether, benzonitrile, and tert-butylphenyl) are synthesized in gram quantities using solid-phase methods. Growing oligomers are attached to a divinylbenzene cross-linked polystyrene support by the 1-aryl-3-propyl-3-(benzyl-supported) triazene moiety. This linkage is obtained by reaction of arenediazonium tetrafluoroborate salts with a n-propylamino-modified Merrifield resin. Condensation strategies are described, producing oligomers with higher yields and simplified procedures compared to solution-phase methods. Terminal acetylene is protected with a trimethylsilyl group. After deprotection of the resin-bound terminal acetylene, an aryl iodide monomer or an aryl iodide-terminated oligomer is coupled to the supported oligomer using a palladium(0) catalyst. The cycle can be repeated to produce sequence-specific oligomers of varying length and functionality. The resulting oligomers are liberated from the polymer support by cleavage of the 1-aryl-3-propyl-3-(benzyl-supported) triazene group by reaction with iodomethane producing an aryl iodide. 相似文献
14.
N.S. Allen G.P. Marshall C. Vasiliou L.M. Moore J.L. Kotecha J. Luc-Gardette B. Valange 《Polymer Degradation and Stability》1988,20(3-4):315-324
The thermal, hydrolytic and photochemical oxidation of blue water pipe material has been studied using Fourier Transform infra-red microscopy, differential scanning calorimetry (DSC) and hydroperoxide analysis. The results indicate that oxidation of the pipe occurs predominantly on the outer surface and to a lesser extent on the bore, often with little or no change in the middle layers, FTIR analysis of microtomed sections of the pipe supports the DSC analysis (oxidation induction time at 200°C—OIT) and indicates leaching and consumption of the polymer antioxidants at the outer surface of the pipe. Oxidation profiles at 80°C in water, as measured using carbonyl index, indicate an unusual hydrolytic oxidation and extraction of the carbonylic oxidation products only at the outer pipe surface to a depth of about 0·5 mm resulting in high hydroperoxidation levels. These oxidation analyses are consistent with density profile changes through the pipe wall. Whilst water is concluded to have an important influence in controlling pipe stability, which, in turn, is governed by the temperature and extractability of the polymer antioxidants, ultraviolet light is also seen to have a similar detrimental effect. The influence of these various degradative parameters on the long-term stability of pipe is discussed with a view to elucidating the mechanisms involved. 相似文献
15.
Abstract The antimalarial drugs, chloroquine, hydroxychloroquine, quinine, quinacrine, amodiaquine and primaquine and the local anaesthetic, dibucaine, were tested for in vitro photosensitizing capability by irradiation with 365 nm UV light in aqueous solutions. The ability of these compounds to photosensitize the oxidation of 2,5-dimethylfuran, histidine, tryptophan or xanthine, and to initiate the free radical polymerization of acrylamide was examined in the pH range 2-12. Chloroquine and hydroxychloroquine show maximal photooxidative behaviour when in the monocation form at pH 9, in contrast to quinine which is extremely efficient as the dication below pH 4. This pattern appears to relate to the fluorescence yield as a function of pH. Chloroquine in the monocation or neutral form was found to undergo dechlorination upon irradiation, and this correlates directly with its ability to initiate photo-polymerization of acrylamide. Quinine also gives rise to small polymerization rates, attributed to photo-ionization in the quinoline ring, yielding a cation radical. Amodiaquine, primaquine and quinacrine do not have significant photochemical activity in aqueous solution. Dibucaine exhibits a strong photosensitizing capability at low pH, similar to quinine. 相似文献
16.
R. A. Dewberry S. R. Salaymeh V. R. Casella F. S. Moore 《Journal of Radioanalytical and Nuclear Chemistry》2006,267(3):515-531
Summary This paper contains a summary of the holdup and material control and accountability (MC&A) assays conducted for the determination
of highly enriched uranium (HEU) in the deactivation and decommissioning (D&D) of the Reactor Fuel Fabrication Facility at
the Savannah River Site (SRS). The facility was used to fabricate HEU fuel assemblies, lithium-aluminum target tubes, neptunium
assemblies, and miscellaneous components for the SRS production reactors. The facility operated for more than 35 years. During
this time thousands of uranium-aluminum alloy (U-Al) production reactor fuel tubes were produced. After the facility ceased
operations in 1995, all of the easily accessible U-Al was removed from the building, and only residual amounts remained. The
bulk of this residue was located in the equipment that generated and handled small U-Al particles and in the exhaust systems
for this equipment (e.g., chip compactor, casting furnaces, log saw, lathes A & B, cyclone separator, Freon?cart, riser crusher,
…, etc). The D&D project is likely to represent an important example for D&D activities across SRS and across the Department
of Energy weapons complex. The Savannah River National Laboratory was tasked to conduct holdup assays to quantify the amount
of HEU on all components removed from the facility prior to placing in solid waste containers. The 235U holdup in any single component of process equipment must not exceed 50 g in order to meet the container limit. This limit
was imposed to meet criticality requirements of the low level solid waste storage vaults. Thus, the holdup measurements were
used as guidance to determine if further decontamination of equipment was needed to ensure that the quantity of 235U did not exceed the 50 g limit and to ensure that the waste met the Waste Acceptance Criteria (WAC) of the solid waste storage
vaults. Since HEU is an accountable nuclear material, the holdupassays and assays of recovered residue were also important
for material control and accountability purposes. In summary, the results of the holdup assays were essential for determining
compliance with the Waste Acceptance Criteria, Material Control & Accountability, and to ensure that administrative criticality
safety controls were not exceeded. This paper discusses theg-ray assay measurements conducted and the modeling of the acquired
data to obtain measured holdup in process equipment, exhaust components, and fixed geometry scrap cans. It also presents development
work required to model new acquisition configurations and to adapt available instrumentation to perform the assays. 相似文献
17.
This Letter describes the amination of 3-bromoisoxazoles by a nucleophilic aromatic substitution reaction. We have found 3-bromoisoxazoles to be inert to substitution under thermal conditions, however, the employment of phosphazene bases under microwave irradiation facilitates the amination process and allows the corresponding 3-aminoisoxazoles to be isolated in moderate yield. 相似文献
18.
During the grinding of quartz, water is adsorbed from the atmosphere, but this water gave no detectable thermal effect on DTA because it was evolved uniformly up to 1000°. However, in conjunction with an iron contaminant, the adsorbed water was involved in an oxidation reaction causing noticeable thermal effects for quartz powdered in a vibration mill constructed of steel parts. When powdered so finely that the - inversion peak at 573° had disappeared, annealing caused a partial redevelopment of the peak but recrystallization of disrupted quartz was too small an effect to give any detectable exothermic peak on DTA.
We are grateful to the Science Research Council for supporting this work. 相似文献
Zusammenfassung Während des Vermahlens von Quartz wird Wasser aus der Atmosphäre adsorbiert, jedoch ergab dieses Wasser keinen nachweisbaren thermischen Effekt in der DTA, da es bis zu 1000° gleichmässig freigesetzt wird. Im Zusammenhang mit einer Eisen-Verunreinigung wurde jedoch das adsorbierte Wasser in eine Oxidationsreaktion einbezogen, welche beim in einer aus Stahlteilen gefertigten Vibrationsmühle zerpulvertem Quartz nachweisbare thermische Effekte verursachten. Wenn so fein pulverisiert wurde, daß der --Inversions-Peak bei 573° verschwunden war, verursachte eine Wärmebehandlung eine teilweise Wiederentwicklung des Peaks, jedoch war die Rekristallisation des zerstörten Quartzes zu geringfügig um einen nachweisbaren exothermen Peak in der DTA-Kurve zu ergeben.
Résumé Lors du broyage du quartz, il se produit une adsorption de l'eau atmosphérique mais cette eau ne donne pas d'effet thermique décelable par ATD car elle se dégage régulièrement jusqu'à 1000°. Cependant, en présence de fer comme contaminant, l'eau adsorbée intervient dans une réaction d'oxydation qui donne des effets thermiques perceptibles dans le cas de quartz pulvérisé dans un vibrobroyeur en acier. Si le quartz est en poudre assez fine pour que le pic d'inversion - à 573° disparaisse, le recuit provoque la réapparition partielle du pic. La recristallisation du quartz est cependant trop faible pour donner un effet exothermique décelable par ATD.
, , 1000°. , , . - 573° , , , - .
We are grateful to the Science Research Council for supporting this work. 相似文献
19.
20.
Incorporation of a pyridine monomer into the backbone of a m-phenylene ethynylene oligomer allows functionalization of the interior binding cavity of the folded oligomer. The basicity of the inwardly directed pyridine moiety was modulated by changing the substituents on the pyridine ring and through oligomer folding, granting access to a pK(a) range of 5-14 in acetonitrile. [reaction: see text] 相似文献