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61.
Manuel Bueno Francisca Zamora Inmaculada Molina Hernn A. Orgueira Oscar Varela Juan A. Galbis 《Journal of polymer science. Part A, Polymer chemistry》1997,35(17):3645-3653
The synthesis of three new stereoregular AB-type polyamides based on D -ribono-1,4-lactone, L -arabinose, and D -xylose has been carried out by the active ester polycondensation method. These polyamides were characterized by elemental analysis, IR and NMR spectroscopies, and powder X-ray diffraction. They displayed optical activity and had a pronounced affinity to water, although they were not soluble in this solvent. The polyamide obtained from D -ribono-1,4-lactone was highly crystalline and yielded films with spherulitic texture. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 3645–3653, 1997 相似文献
62.
Inmaculada Molina Pinilla Manuel Bueno Martínez Francisca Zamora Mata Juan A. Galbis 《Journal of polymer science. Part A, Polymer chemistry》1998,36(1):67-77
Two poly(ester amides) containing three methoxy groups stereoregularly attached to the main chain have been prepared by using naturally occurring L -arabinose and D -xylose as the starting materials. The polymers were prepared by the active ester polycondensation method and characterized by elemental analysis, IR, and 1H- and 13C-NMR spectroscopies. Both viscosimetry and GPC were used to estimate the molecular weights. The polymers are hydrophilic, one of them being water soluble, and exhibited moderate optical activity. Thermal and X-ray diffraction studies revealed that they are slightly crystalline and stable up to 250°C under nitrogen. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 67–77, 1998 相似文献
63.
Cabrera Pérez Laura C. Padilla-Martínez Itzia I. Cruz Alejandro Correa Basurto José Miliar García Ángel Hernández Zavala Argelia A. Gómez López Modesto Rosales Hernández Martha C. 《Molecular diversity》2020,24(4):1-14
Molecular Diversity - 11-Beta hydroxysteroid dehydrogenase type 1 (11β-HSD1) regulates cortisol levels mainly in adipose, hepatic and brain tissues. There is a relationship between the high... 相似文献
64.
On-line characterisation of apple polyphenols by liquid chromatography coupled with mass spectrometry and ultraviolet absorbance detection 总被引:5,自引:0,他引:5
Alonso-Salces RM Ndjoko K Queiroz EF Ioset JR Hostettmann K Berrueta LA Gallo B Vicente F 《Journal of chromatography. A》2004,1046(1-2):89-100
Apple polyphenols were characterised by means of hyphenated techniques such as HPLC coupled to UV photodiode array detection (LC-DAD) and to mass spectrometry (LC-MS). LC-MS using atmospheric pressure ionisation (APCI) in the positive ion mode provided the molecular weight, the number of hydroxyl groups, the number of sugars and an idea about the substitution pattern of the polyphenols. LC-DAD with postcolumn addition of UV shift reagents afforded precise structural information about the position of the free hydroxyl groups in the polyphenolic nucleus. Five isorhamnetin glycosides, two hydroxyphloretin glycosides and quercetin were reported in apple peel for the first time. Postcolumn addition of UV shift reagents in LC-DAD analysis confirmed the presence of isorhamnetin glycosides and not the isomeric glycosides of rhamnetin. Moreover, isorhamnetin-3-O-rhamnoglucoside was identified unambiguously by comparison with a standard. These results are relevant not only from a chemotaxonomic point of view, but also in the control of authenticity of fruit derived products in order to detect fraudulent admixtures. 相似文献
65.
Belén Begines Francisca Zamora Elena Benito Mª de Gracia García‐Martín Juan A. Galbis 《Journal of polymer science. Part A, Polymer chemistry》2012,50(22):4638-4646
Linear polyurethanes based on sugar monomers having D ‐gluco, galacto, and D ‐manno configurations and their secondary hydroxyl groups protected as bicyclic acetals, have been prepared by polyaddition reaction of these diol monomers to hexamethylene diisocyanate ( HMDI ) and 4,4′‐methylene‐bis(phenyl isocyanate) ( MDI ). The new polyurethanes seem to be amorphous materials, except that obtained from 2,3:4,5‐di‐O‐methylene‐galactitol and HMDI. Weight‐average molecular weights, determined by GPC, were in the range 16,000–115,200. TGA analyses indicated that the thermal stability of these bicyclic polyurethanes is comparable to those based on the isosorbide; both the onset and the maximum rate decomposition temperatures increased significantly with respect to the polyurethanes based on acyclic sugar monomers. The presence of the acetalized alditol units in the polyurethanes also increased the Tgs as compared with their acyclic analogs. Deacetalization of the polyurethanes containing di‐O‐isopropylidene‐D ‐mannitol units yielded the polyhydroxylated polymers in good yields, without apparent degradation of the polymer chain. These hydroxylated polymers showed an enhanced hydrophilicity and degradability and lower Tgs and thermal stability than their parent acetalized polyurethanes. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
66.
Belén Begines Francisca Zamora Isaac Roffé Manuel Mancera Juan A. Galbis 《Journal of polymer science. Part A, Polymer chemistry》2011,49(9):1953-1961
Novel linear homogeneous polyurethanes and polyureas with enhanced hydrophilic character have been successfully prepared from sugar‐based monomers having their hydroxyl groups free or partially protected. By the reaction of primary hydroxyl groups of xylitol with dimethyl hexamethylene dicarbamate (HMDC) or di‐tert‐butyl‐4,4′‐diphenyl methyl dicarbamate (MDC), two new linear semicrystalline polyurethanes [PU(X‐HMDC) and PU(X‐MDC)] have been prepared. Likewise, by the reaction of xylitol with the analogous diisocyanates hexamethylene diisocyanate (HMDI) or 4,4′‐methylenebis(phenyl isocyanate) (MDI), similar polyurethanes [PU(X‐HMDI) and PU(X‐MDI)] were obtained. However, these latter polyurethanes present some degree of crosslinking because of the higher reactivity of the diisocyanate comonomers. Linear hydrophilic polyureas having free hydroxyl groups joined to the main chain have also been prepared by the reaction of the same diisocyanates (HMDI and MDI) with 1,6‐diamino‐1,6‐dideoxy‐D ‐mannitol and 1,6‐diamino‐1,6‐dideoxy‐3:4‐O‐isopropylidene‐D ‐mannitol. As far as we are aware, this kind of polyhydroxylated polyurea has not been previously described in the literature. The new polymers were characterized by standard methods (elemental analyses, gel permeation chromatography, IR, and NMR). The polyurethanes were hydrolytically degradable under physiological conditions, in contrast with less‐hydrophilic linear polyurethanes previously described. The thermal properties of the novel polymers were investigated by thermogravimetric analysis and differential scanning calorimetry. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
67.
Víctor Tena Pérez Ángel L. Fuentes de Arriba Laura M. Monleón Luis Simón Omayra H. Rubio Francisca Sanz Joaquín R. Morán 《Tetrahedron》2014
Borohydride reduction of salicylaldehyde imines yields surprisingly a cyclic boramide. This is a fairly stable compound, and X-ray analysis shows it has a tetrahedral boron atom. Mechanistic studies show a reaction pathway through an oxazaborinane intermediate. The reaction also works with halogen substituted salicylaldehydes and for the preparation of non-symmetrical boramides. 相似文献
68.
The effect of sulfonation on polysulfone regarding its electrical properties is studied and discussed. In addition to the effect of percentage of sulfonation, the thickness of thin films and the ultraviolet (UV) treatment also were evaluated and reported. The results indicate that percentage of sulfonation is the most important effect, even over thickness. As the sulfonation percentage was increased, better electrical performance (fill factor and power conversion efficiency) was obtained because the sulfonate groups impart a kind of vacancy into the polymer structure, showing comparable energy level to that of conventional poly (3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS).In addition, the UV treatment not only cleans the film's surface but also polarizes the polymeric's surface improving the polysulfone performance, which was 24% better, at least, respect to that obtained without UV treatment. The obtained results open the possibility to optimize sulfonated polysulfones that could be used in inverted hybrid perovskite solar cells. 相似文献
69.
A family of pincer-like receptors (2-5) has been synthesized and tested for the NMR enantiodiscrimination (CSA) of chiral carboxylic acids. Starting from a previous design (1), different structural variables have been mapped on the receptor frame. The splitting of the signals of the acids upon the addition of the CSAs largely depends on these structural variables. Thus, we concluded that the C2 symmetrical pyridine-2,6-biscarboxamide moiety is a key structural feature for the efficiency of the CSA. Structural studies by NMR and molecular modeling showed that this moiety promotes the U-shape-folded pincer-like conformation by intramolecular H-bonds. On the other hand, we also observed that the cyclohexane-1,2-diamine derivative 5 is a more versatile CSA than its cyclopentane analogue 1, as 5 shows a better performance for more structurally different acids. However, the original cyclopentane derivative (1) remained the best for the arylpropionic acids. Finally, combination of NMR and modeling studies allowed us to propose a reasonable model for the interaction and, accordingly, for the observed NMR enantiodiscrimination. 相似文献
70.
Verónica Llaneza Ismael Rodea-Palomares Zuo Zhou Roberto Rosal Francisca Fernández-Pina Jean-Claude J. Bonzongo 《Journal of nanoparticle research》2016,18(8):235
The efficiency of zero-valent iron particles used in the remediation of contaminated groundwater has, with the emergence of nanotechnology, stimulated interest on the use of nano-size particles to take advantage of high-specific surface area and reactivity characteristics of nanoparticles (NPs). Accordingly, engineered iron-NPs are among the most widely used nanomaterials for in situ remediation. However, while several ecotoxicity studies have been conducted to investigate the adverse impacts of these NPs on aquatic organisms, research on the implications of spent iron-based NPs is lacking. In this study, a comparative approach is used, in which the biological effects of three iron-based NPs (Fe3O4 and γ-Fe2O3 NPs with particle sizes ranging from 20 to 50 nm, and Fe0-NPs with an average particle size of 40 nm) on Raphidocelis subcapitata (formely known as Pseudokirchneriella subcapitata) and Daphnia magna were investigated using both as-prepared and pollutant-doped Fe-based NPs. For the latter, arsenic (As) was used as example sorbed pollutant. The results show that improved degree of NP dispersion by use of polyvinylpyrrolidone overlapped with both increased arsenic adsorption capacity and toxicity to the tested organisms. For R. subcapitata, Fe-oxide NPs were more toxic than Fe0-NPs, due primarily to differences in the degree of NPs aggregation and ability to produce reactive oxygen species. For the invertebrate D. magna, a similar trend of biological responses was observed, except that sorption of As to Fe0-NPs significantly increased the toxic response when compared to R. subcapitata. Overall, these findings point to the need for research on downstream implications of NP-pollutant complexes generated during water treatment by injection of NPs into aquatic systems. 相似文献