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Barberá J Puig L Romero P Serrano JL Sierra T 《Journal of the American Chemical Society》2005,127(1):458-464
The work described here concerns a challenge of general interest in supramolecular chemistry: the achievement of chiral helical organizations with controlled structures. This work provides a strategy to obtain supramolecular polymers in which a chiral helical conformation has been induced by a noncovalent association, that is, through hydrogen bonding. Polycatenar 2,4,6-triarylamino-1,3,5-triazines, which organize into columnar mesophases and are susceptible to H-bonding interactions, were chosen as a starting point to build up the chiral supramolecular structure. The stacking of these mesogens has been forced to wind in a helical way by means of H-bond association with (R)-3-methyladipic acid, within the mesophase. The optically active columnar organization has been studied in depth by optical microscopy, differential scanning calorimetry (DSC), X-ray diffraction, and circular dichroism. Formation of stable complexes between the triazine units and (R)-3-methyladipic acid has also been investigated by means of NMR diffusion-ordered spectroscopy (DOSY) experiments in chloroform. 相似文献
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María?Belén?Sierra Marcela?A.?Morini Pablo?C.?SchulzEmail author María?Luján?Ferreira 《Colloid and polymer science》2005,283(9):1016-1024
Following the studies on the effect of double bonds in the surfactant hydrophobic tail on the formation of mixed surfactant aggregates, we studied the viscosity and density of the system Sodium 10-undecenoate (SUD)–decyltrimethylammonium bromide (DTAB)–water. We found that the partial molar volume (pmv) and intrinsic viscosity of both, micellised and unmicellised mixtures, are non-ideal, dependent on the mixture composition and related to structural changes in micelles. These phenomena are caused by the presence of the double bond at the distal extreme of the SUD molecule, which has some affinity with water by formation of hydrogen bonds. In particular, as far as we know, this is the first report on non-ideal behavior of the pmv in mixed micelles. 相似文献
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The aqueous cationic system sodium undecenoate-dodecyltrimethylammonium bromide at low concentration
Maria?Belén?Sierra Marcela?A.?Morini Pablo?C.?SchulzEmail author 《Colloid and polymer science》2004,282(6):633-641
The aqueous sodium undecenoate (SUD) –dodecyltrimethylammonium bromide (DTAB) catanionic system was studied at low concentration. The system did not precipitate, even at a 1:1 SUD:DTAB proportion, but showed the formation of a coacervate in a range of surfactant mixture compositions. Micelles have a preferential composition of 0.37 mole fraction of SUD. This behavior is attributed to the presence of the double bond at the distal extreme of the SUD molecule, which can form hydrogen bonds with water. Consequently, the –CH=CH2 group is situated at the interface between the hydrocarbon micelle core and water, reducing the interfacial free energy. Structural computations demonstrate that the mentioned SUD proportion produces complete coverage of the micelle surface by the double bonds. 相似文献
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The available and total niacin evolution during maturation of yellow pea lupine (Lupinus luteus L., cv. Juno), pea (Pisum sativum L., cv. Ergo), faba bean (Vicia faba sp. minor Harz, cv. Tibo) and in germinated and high-pressure heated peas (Pisum sativum L., cv. Esla) have been determined by capillary electrophoresis (CE). The results have been compared with those obtained by high-performance liquid chromatography (HPLC). The values obtained by CE were similar to those obtained by HPLC. Maturation of seeds significantly reduced the available and total niacin content in legumes. The available/total niacin ratio during seed maturation depends on the type of legume. In faba beans and peas, a reduction was observed which was more pronounced in the case of peas. For lupine seeds, the ripening produced an increase (34%) in the available/total niacin ratio 50 days after flowering (DAF). Pea germination produced an overall increase in available and total niacin content although the available/total niacin ratio decreased. High pressure heating of pea yielded an increase in the available niacin content and available/total niacin ratio but the total niacin content did not change. 相似文献
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LoSecco JM Bionta RM Biewitt G Bratton CB Casper D Chrysicopoulou P Claus R Cortez BG Errede S Foster GW Gajewski W Ganezer KS Goldhaber M Haines TJ Jones TW Kielczewska D Kropp WR Learned JG Lehmann E Park HS Reines F Schultz J Seidel S Shumard E Sinclair D Sobel HW Stone JL Sulak L Svoboda R van der Velde JC Wuest C 《Physical review letters》1985,54(21):2299-2301