Synthesis of 2-substituted 4,5-dihydro-4-oxo-3-furancarboxylates using acylative intramolecular cyclization of sulfonium salts

A simple and efficient synthesis of 4,5-dihydro-4-oxo-3-furancarboxylates using an acylative intramolecular cyclization of sulfonium salts is described. The reaction involved the efficient formation of a mixed anhydride between a linear carboxylic acid and trifluoroacetic anhydride in the presence of N-methylimidazole, followed by the sequential conversion into a highly reactive acylammonium species in situ. This procedure is easily handled, uses readily available inexpensive reagents, and provides a variety of 2-substituted 4,5-dihydro-4-oxo-3-furancarboxylates.     

Solubility of Anthraquinone Derivatives in Supercritical Carbon Dioxide: New Correlations

Solubility of several anthraquinone derivatives in supercritical carbon dioxide was readily available in the literature, but correcting ability of the existing models was poor. Therefore, in this work, two new models have been developed for better correlation based on solid–liquid phase equilibria. The new model has five adjustable parameters correlating the solubility isotherms as a function of temperature. The accuracy of the proposed models was evaluated by correlating 25 binary systems. The proposed models observed provide the best overall correlations. The overall deviation between the experimental and the correlated results was less than 11.46% in averaged absolute relative deviation (AARD). Moreover, exiting solubility models were also evaluated for all the compounds for the comparison purpose.     

Visual observations of flow structure and melting front morphology in horizontal ice plate melting from above into a mixture

Visual observations reveal a complicated flow in the liquid melt and a melting front configuration resulting from horizontal ice plate melting from above into a 20 wt% calcium chloride aqueous solution. The initial temperature of the ice plate and the mixture are both −5°C. Small scale “mountain and valley” structures (∼1 mm) appear on the flat melting front just after melting begins, which have been called “sharkskin”. Innumerable upward and downward flows appear near the sharkskin and are controlled by its “mountain and valley” structure. These typical flows will considerably promote the melting of the ice plate to be 30% larger as compared to the numerically predicted results assuming a flat melting front (i.e., without the sharkskin), and also by three times larger compared with the results for melting from below.     

Polymer electrolyte membranes based on polystyrenes with phosphonic acid via long alkyl side chains

A series of polystyrenes with phosphonic acid ( 5 ) via long alkyl side chains (4, 6, and 8 methylene units) were prepared by the radical polymerization of the corresponding diethyl ω‐(4‐vinylphenoxy)alkylphosphonates, followed by the hydrolysis with trimethylsilyl bromide. The resulting phosphonated polystyrene membranes had a high oxidative stability against Fenton's reagent at room temperature. The membranes prepared from 5 exhibited a very low water uptake, similar to that of Nafion 117 over the wide range of 30 to 80% relative humidity (RH). The proton conductivities of these membranes are lower than that of Nafion 117 in the range of 30 to 90% RH, but comparable or higher than those of the reported phosphonated polymers with higher IEC values, such as the phosphonated poly(N‐phenylacrylamide) (PDPAA, IEC: 6.72 mequiv/g) and fluorinated polymers with pendant phosphonic acids (M47, IEC: 8.5 mequiv/g), at low RH conditions despite the much lower IEC values (3.0–3.8 mequiv/g) of these membranes. These results suggest that the flexible pendant side chains of 5 would contribute to the formation of hydrogen‐bonding networks by considering the very low water uptake of these polymers. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Synthesis of end‐functionalized polyethers by phosphazene base‐catalyzed ring‐opening polymerization of 1,2‐butylene oxide and glycidyl ether

For the living ring‐opening polymerization (ROP) of epoxy monomers, the catalytic activity of organic superbases, tert‐butylimino‐tris(dimethylamino)phosphorane, 1‐tert‐butyl‐2,2,4,4,4‐pentakis(dimethylamino)‐2Λ⁵,4Λ⁵‐catenadi(phosphazene), 2,8,9‐triisobutyl‐2,5,8,9‐tetraaza‐1‐phosphabicyclo[3.3.3]undecane, and 1‐tert‐butyl‐4,4,4‐tris(dimethylamino)‐2,2‐bis[tris(dimethylamino)phosphoranylidenamino]‐2Λ⁵,4Λ⁵‐catenadi(phosphazene) (t‐Bu‐P₄), was confirmed. Among these superbases, only t‐Bu‐P₄ showed catalytic activity for the ROP of 1,2‐butylene oxide (BO) to afford poly(1,2‐butylene oxide) (PBO) with predicted molecular weight and narrow molecular weight distribution. The results of the kinetic, post‐polymerization experiments, and MALDI‐TOF MS measurement revealed that the t‐Bu‐P₄‐catalyzed ROP of BO proceeded in a living manner in which the alcohol acted as the initiator. This alcohol/t‐Bu‐P₄ system was applicable to the glycidol derivatives, such as benzyl glycidyl ether (BnGE) and t‐butyl glycidyl ether, to afford well‐defined protected polyglycidols. The α‐functionalized polyethers could be obtained using different functionalized initiators, such as 4‐vinylbenzyl alcohol, 5‐hexen‐1‐ol, and 6‐azide‐1‐hexanol. In addition, the well‐defined cyclic‐PBO and PBnGE were successfully synthesized using the combination of t‐Bu‐P₄‐catalyzed ROP and click cyclization. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Measuring grain rotation at the nanoscale

In this paper, we introduced a method to measure grain rotation of nanomaterials under external stress using a high pressure diamond anvil cell and the Laue microdiffraction technique at a synchrotron facility. We used tungsten carbide marker crystals to investigate grain rotation activities of 3 and 500?nm nickel media. Our results show that the grain rotation of 3 and 500?nm nickel nanocrystals increase with pressure and finally rotation of 500?nm nickel tends to stop at a lower pressure/stress level than 3?nm nickel. 3?nm nickel nanocrystals show a higher rotation magnitude than 500?nm nickel nanocrystals. Our measurements show an effective method to study the grain rotation of nanomaterials especially in ultrafine nanocrystals.