Supramolecular gels are soft materials formed mainly by low molecular weight units held together by intermolecular interactions. Stabilizing these kinds of materials is quite a challenge due to the influence of multiple factors interfering with the integrity of the supramolecular structure. In our previous studies, we have shown that the aminocarbohydrate meglumine (MEG) interacts with organic acids by ion-pairing leading to the formation of MEG–carboxylate adducts. These adducts undergo supramolecular polymerization by heat treatment, but the macromolecular assembly was stable for a short period due to hydrogen bond (H-bond) breakup. Herein, we attempt to study the influence of hydrophobic building blocks on the formation of these compounds aiming to stabilize H-bonds to produce polymerizable supra-amphiphiles in water. Oleic acid and stearic acid are two analogous fatty acids differing only in the presence of unsaturation that were used in our studies. Results demonstrated that the presence of unsaturation hinders gelation in water by interfering with the self-assembly behavior of supra-amphiphiles. Thus, unsaturated supra-amphiphiles behave like traditional surfactants and gelify water at high concentrations (above 30% w/w). On the other hand, supramolecular gels with a polymer-like behavior could be produced with a saturated supra-amphiphile in water (above 4% w/w). The material was characterized by a lamellar arrangement that facilitates the alignment of H-bonds necessary to stabilize the self-assembled structure. These results have pivotal importance on the design of polymerizable supra-amphiphiles and demonstrate that the double bond of hydrophobic building blocks is an important design factor to be considered by scientists studying similar materials. 相似文献
In this study, the preparation by grafting of amino-functionalized SBA-15 molecular sieves was carried out. Amino-functionalized molecular sieves were synthesized using a silane coupling agent and different types of amination reagents which react with modified SBA-15. These composites were characterized by FT-IR spectroscopy, X-ray diffraction at low angles, nitrogen physisorption at 77 K, and evaluated by the adsorption of CO2 and its temperature-programmed desorption—TPD. Thermal stability was investigated by TGA and DTA methods. In the view of a possible use of these amino-functionalized molecular sieves as sorbents for CO2 removal, their adsorption–desorption properties towards CO2 were also investigated by the TPD method. The mass loss of amino-functionalized molecular sieves above 215 °C was due to the oxidation and decomposition of amino propyl functional groups. This means that these composites could be used for adsorption of CO2 at temperatures below 215 °C. The adsorption of CO2 and its temperature programmed desorption using thermogravimetry were studied for amino-functionalized molecular sieves at 60 °C. The evolved gases during the adsorption–desorption of CO2 on amino-functionalized molecular sieves were identified by online mass spectrometry coupled with thermogravimetry. CO2 adsorption isotherms of functionalized samples at 60 °C showed that both the adsorption capacity (mg CO2/g adsorbent) and the efficiency of amino groups (mol CO2/mol NH2) depend on the type of amination reagents and the amount of organic compound used.
Journal of Thermal Analysis and Calorimetry - The food-colouring dye tartrazine is a significant additive and in the same time a biologically active material. Thermal behaviour of trisodium... 相似文献
Journal of Thermal Analysis and Calorimetry - A novel series of complexes ML(ClO4)·nH2O (M: Co, Ni, Cu, Zn; HL: 2-[(E)-(1H-1,2,4-triazol-3-ylimino)methyl]phenol) have been synthesized and... 相似文献
Na2Ti3O7 ceramic materials have been widely used in sodium-ion battery applications with relative good results; however, there are still several studies that might be carried out in the improvement of the Na2Ti3O7 properties and the overall batteries’ performance. In this direction, we used sonochemical method following a thermal treatment in order to synthetized pure phase Na2Ti3O7 nanopowders. X-ray diffraction characterization revealed that Na2Ti3O7 is the primary phase in nanopowders and ceramic sample; although, a high level of amorphization was observed in the sonicated nanopowder without heat treatment process. Nanopowder-prepared ceramic sample showed a crystallite size of 50 nm after sintering at 900 °C for 1 h. The specific surface area, pore volume, and pore size were obtained from the B.E.T. measurements, being 51 m2 g?1, 0.07 cm3 g?1, and 55 Å, respectively. The capacitance values of the nanopowder-prepared ceramic sample were in the order of microfarad. The total energy of the system was used to determine relaxation time of the sample (τ0 = 31 ms). 相似文献
Thermoanalytical techniques, especially temperature-programmed reduction (TPR), were employed for the characterization of oxidic precursors of molybdenum-based catalysts, sulfides derived from them, and three thiomolybdate compounds, employed as models or precursors of hydrodesulfurization atalysts. Correlations were found between TPR data and the presence of single and mixed oxides of Mo and Ni, Co or Fe, as demonstrated by XRD. The same phases and the thiomolybdates were shown to be present in supported catalytic precursors. Differences between the reducibilities of the mixed oxides of Ni-Mo, Co-Mo and Fe-Mo are easily appreciated from TPR, including those of the - and - polymorphic modifications of NiMoO4.Support from Venezuela's Consejo Nacional de Investigations Científicas y Tecnológicas (CONICIT) and the International Activities Program of the American Chemical Society is gratefully acknowledged. The use of the TPR/TPD 2900 instrument was made possible by a generous loan of Micromeritics. Special thanks to my students and coworkers, who co-authored the publications cited in the list of references. 相似文献
We review some exact results for the motion of a tagged particle in simple models. Then, we study the density dependence of the self-diffusion coefficientDN() in lattice systems with simple symmetric exclusion in which the particles can jump, with equal rates, to a set ofN neighboring sites. We obtain positive upper and lower bounds onFN()=N{(1–)–[DN()/DN(0)]}/[(1–)]x for [0, 1]. Computer simulations for the square, triangular, and one-dimensional lattices suggest thatFN becomes effectively independent ofN forN20. 相似文献
Bernoullicity is the strongest mixing property that a measure-theoretic dynamical system can have. This is known to be intimately connected to the so-called metric on processes, introduced by Ornstein. In this paper, we consider families of measures arising in a number of contexts and give conditions under which the measures depend -continuously on the parameters. At points where there is -continuity, it is often straightforward to establish that the measures have the Bernoulli property.
Polyaminobismaleimides (PAMBI) with diphenyl methane, diphenyl ether and hexamethylene segments were synthesized according
to Michael type addition reaction. The modification of PAMBIs with 2-glycidyl-phenyl-ether (GPE) was performed in order to
ameliorate the toughness of the products. Dynamic mechanical analysis allowed the study of the processes that concur in the
material through curing by tracking the storage modulus (E′) and loss factor (tanδ) changes. The small drop of E′ with increasing temperature in the glass transition region argues for crosslinked structures. The viscoelastic behavior
revealed complex processes, i.e., overlapping of glass transition temperature range with intra-and inter-crosslinking. 相似文献
Aminoglycosides are highly potent, broad-spectrum antibiotics that exert their bactericidal therapeutic effect by selectively binding to the decoding aminoacyl site (A-site) of the bacterial 16 S rRNA, thereby interfering with translational fidelity during protein synthesis. The appearance of bacterial strains resistant to these drugs, as well as their relative toxicity, have inspired extensive searches towards the goal of obtaining novel molecular designs with improved antibacterial activity and reduced toxicity. In the last few years, a new, aminoglycoside dependent therapeutic approach for the treatment of certain human genetic diseases has been identified. These treatments rely on the ability of certain aminoglycosides to induce mammalian ribosomes to readthrough premature stop codon mutations. This new and challenging task has introduced fresh research avenues in the field of aminoglycoside research. Recent observations and current challenges in the design of aminoglycosides with improved antibacterial activity and the treatment of human genetic diseases are discussed. 相似文献