An N-heterocycle (tetrazole)-stabilized pseudocyclic λ3-iodane was synthesized and its thermal stability and redox activity were studied. Simultaneous thermogravimetric analysis and differential scanning calorimetry revealed that the polyvalent iodine compound started to degrade at 127 °C and showed a notable exothermic decomposition peak at 147 °C, which was markedly more pronounced than the parent tetrazole with monovalent iodine. The reduction potential was determined by cyclic voltammetry to be ?0.38 V vs AgNO3|Ag in dimethyl sulfoxide at a scan rate of 0.02 V/s. The oxidative power of the polyvalent iodine compound was demonstrated by conducting oxidation of thioanisole to sulfoxide and oxidative dimerization of thiobenzamide to 3,5-diphenyl-1,2,4-thiadiazole. 相似文献
DDFT is applied to phase formation in homopolymer/copolymer blends in which the copolymer is extremely disperse with a uniform chemical composition distribution. Such systems develop a core/shell structure with a thick interface. This study is motivated by peculiarities in the phase evolution of industrial PP high‐impact copolymers. It is demonstrated that it is possible to reach time and length scales of relevance for realistic industrial blend systems. A rational method for improving the numerical efficiency of the calculations is presented. The model can be applied to a variety of industrially relevant systems with similar “random chemistry” or extreme copolymer dispersity in coatings, crude oil recovery systems, food emulsions, and so forth.
The hydrates [Na2(H2O)3(Htba)2] (1) and [Na2(H2O)4(Htba)2] (2), where H2tba is 2-thiobarbituric acid, were obtained under different thermal conditions from aqueous solutions and were structurally characterized. The molecular and supramolecular structures were compared to the known structure of [Na2(H2O)5(Htba)2] (3). In polymeric 1–3, the Htba? ions are linked to Na+ through O and S forming octahedra. The decrease of the number of coordination water molecules led to an increase of the total number of bridge ligands (μ2-H2O, Htba?) and a change of the Htba? coordination. These factors induced higher distortion of the octahedra. It was assumed that hydrates, with a different number of coordinated water molecules, are more probable when the central metal has weaker bonds with O water molecules and with other ligands. The net topologies of 1–3 were compared. Thermal decomposition and IR spectra were analyzed for 1 and 2. 相似文献
Polymers bearing activated aziridine groups are attractive precursors to α‐substituted‐β‐amino‐functionalized materials due to the enhanced reactivity of the pendant aziridine functionalities toward ring‐opening by nucleophiles. Two aziridine‐containing styrenic monomers, 2‐(4‐vinylphenyl)aziridine (VPA) and N‐mesyl‐2‐(4‐vinylphenyl)aziridine (NMVPA), were polymerized under a variety of reversible deactivation radical polymerization conditions. Low‐catalyst‐concentration atom transfer radical polymerization (LCC‐ATRP) and reversible addition‐fragmentation chain‐transfer (RAFT) polymerization were ineffective at producing well‐defined polymers from VPA due to side reactions between the aziridine functionalities and the agents controlling the polymerizations (catalysts or chain transfer agents). PolyVPA produced under nitroxide‐mediated polymerization (NMP) conditions had narrow molecular weight distribution at low to moderate conversions of monomer, but branched and eventually cross‐linked polymers were formed at higher conversions due to ring‐opening reactions of the aziridine groups. Most of these undesirable side reactions were eliminated by attaching a methanesulfonyl (mesyl) group to the aziridine nitrogen atom, and well‐defined linear homopolymers with targeted molecular weights were realized from NMVPA under RAFT and NMP conditions; however, side reactions between the aziridine groups and the catalyst in LCC‐ATRP still occured and the polymerization was uncontrolled using this technique.
We prove that every continuum of weight is a continuous image of the Cech-Stone-remainder of the real line. It follows that under the remainder of the half line is universal among the continua of weight -- universal in the `mapping onto' sense.
We complement this result by showing that 1) under every continuum of weight less than is a continuous image of , 2) in the Cohen model the long segment of length is not a continuous image of , and 3) implies that is not a continuous image of , whenever is a -saturated ultrafilter.
We also show that a universal continuum can be gotten from a -saturated ultrafilter on , and that it is consistent that there is no universal continuum of weight .
