共查询到20条相似文献,搜索用时 15 毫秒
1.
A "light-triggerable" azobenzene amine derivative (additive 1) was synthesized and then introduced into organogels of 12-hydroxystearic acid (HSA) in the molar ratio of 1:3. The organogels (HSA/1) consisting of additive 1 and HSA were analyzed by (1)H nuclear magnetic resonance (NMR), Fourier transform-infrared (FT-IR), and X-ray diffraction (XRD). The homogeneity of the gel networks was observed using field emission scanning electron microscopy (FE-SEM). Additive 1 formed a complex with HSA in HSA organogels due to salification between the terminal amine group of additive 1 and the carboxylic acid group of HSA. Additive 1 in the gels of HSA/1 showed the potential for photo-isomerization, and we achieved a reversible control of HSA/1 sol-gel transition in toluene by the alternating irradiation with UV and visible light. Interestingly, the opposite phenomenon was observed in CHCl(3) system, namely, the orange solution of HSA/1 in CHCl(3) was turned to a red-transparent gel by exposure to UV light. 相似文献
2.
Yuehui Hou Tao Sun Feifei Xin Pengyao Xing Shangyang Li Aiyou Hao 《Journal of inclusion phenomena and macrocyclic chemistry》2014,79(1-2):133-140
A unique transformation from a heat-set organogel to a room-temperature organogel induced by ethanol (EtOH) was reported here. When the system containing β-cyclodextrin, 4,4′-isopropylidenediphenol, N,N-dimethylacetamide and LiCl was heated to the gelling temperature (T gel), a heat-set organogel would be formed. In contrast, a semitransparent organogel (room-temperature organogel) could be obtained by injecting EtOH into the system at ambient temperature. In this transformation process, EtOH played a role in the formation of hydrogen bonds, which was critical for the self-assembly. The influence of other guest molecules, solvents and alcohols on this transformation was also investigated. These organogels were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction, thermal gravity analysis and differential thermal gravity. Further, the formation mechanism of the organogels was proposed based on the above measurements. 相似文献
3.
This paper compares and contrasts the behavior of two different gelators using rheological and neutron scattering methods. The flow properties of a steroid-made paramagnetic organogel in cyclohexane are presented. The original gelator STNO is important in the class of organogels as being one of the most documented and as such is a good candidate for comparisons with another reference system, the 12-hydroxy stearic acid (HSA) gel. The linear viscoelastic regime of deformations of STNO gels is identified and analyzed in the context of self-assembled fibrillar networks. The linear elasticity scales with the concentration as G′ α C2 similarly with HSA organogels, and both systems can be considered as cellular materials. Rheological and neutron scattering experiments show that the kinetics of gel formation exhibits long equilibration times corresponding to the elaboration of entangled fibrillar aggregates. Comparison of the linear elasticities between STNO and HSA gels demonstrates that HSA gels are much more stiffer (G′HSA/G′STNO∼2700). Contributions from the cross-sectional sizes, the mesh size of the networks, the solubility concentrations, and the Young's modulus of the materials are discussed. Non-linear flow properties are also compared using thixotropic loops. They indicate that the transduction of the chirality from the molecular to the supramolecular stages is more efficient with STNO gels having strong chiral junction zones. Simplified scattering and optical protocols are proposed to facilitate comparisons between different organogels. 相似文献
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5.
Wendy J. Shaw Yongsheng Chen John Linehan Tom Bitterwolf 《Journal of organometallic chemistry》2008,693(12):2111-2118
A recoverable, water soluble, hydrogenation catalyst was synthesized by reacting poly-N-isopropylacrylamide containing a terminal amino group (H2N-CH2CH2-S-pNIPAAm) with [Rh(CO)2Cl]2 in organic solvents to form the square planar rhodium complex (Rh(CO)2Cl(H2N-CH2CH2-S-pNIPAAm)). The catalyst-ligand structure was characterized using in situ multinuclear NMR, XAFS and IR spectroscopic methods. Model complexes containing glycine (H2NCH2COOH), cysteamine (H2NCH2CH2SH) and methionine methyl ester (H2NCH(CH2CH2SCH3)COOCH3) ligands were studied to aid in the interpretation of the coordination sphere of the rhodium catalyst. The spectroscopic data revealed a switch in ligation from the amine bound (Rh-NH2-CH2CH2-S-pNIPAAm) to the thioether bound (Rh-S(-CH2CH2NH2)(-pNIPAAm)) rhodium when the complex was dissolved in water. The evolution of the structure of the rhodium complex dissolved in water was followed by XAFS. The structure changed from the expected monomeric complex to form a rhodium cluster of up to four rhodium atoms containing one SRR′ ligand and one CO ligand per rhodium center. No metallic rhodium was observed during this transformation. The rhodium-rhodium interactions were disrupted when an alkene (3-butenol) was added to the aqueous solution. The kinetics of the hydrogenation reaction were measured using a novel high-pressure flow-through NMR system and the catalyst was found to have a TOF of 3000/Rh/h at 25 °C for the hydrogenation of 3-butenol in water. 相似文献
6.
Eastoe J Sánchez-Dominguez M Wyatt P Heenan RK 《Chemical communications (Cambridge, England)》2004,(22):2608-2609
A photo-responsive organogel has been made by addition of a novel stilbene-containing photo-surfactant to toluene: exposure to UV light led to a gel-to-sol transition with spatial control. 相似文献
7.
We have found that compound 1 forms organogels in appropriate organic solvents and the resultant gel phase exhibits unusual emission properties arising from the excimer formation. 相似文献
8.
Yuangang Li 《Tetrahedron》2007,63(31):7468-7473
New l-glutamic acid based dendritic compounds: N-(2-naphthacarbonyl)-l-glutamic acid diethyl ester (NGE) and N-(2-naphthacarbonyl)-1,5-bis(l-glutamic acid diethyl ester)-l-glutamic diamide (NBGE) were designed. Although NGE could not form any gels in common solvents, NBGE could form stable gels in hexane, toluene, and water under ultrasound. Three dimensional network structures composed of fibers with various diameters were observed in the gel by SEM and TEM. FTIR spectral measurement revealed that ultrasound during cooling of the solution could destroy some of the hydrogen bond interactions and caused the gel formation. In solution, no CD signal was detected because the naphthyl chromophore is far from the chiral center. In the gel, however, CD signals assigned to the naphthyl group were observed, which indicated that the chirality of the chiral center could be transferred to the chromophore in the supramolecular organogel system. 相似文献
9.
A bis-urea derived gelator 1 was synthesised with a high yield via a simple organic reaction. The gelator could form organogel in four kinds of solvents. The organogels obtained from four kinds of solvents were systematically investigated by FESEM, UV–Vis, PL, IR, XRD and water contact angle experiments. It was interesting that the self-assembly process of gelator 1 could be tuned by solvents. The film structure and fibre were formed in different solvents. At the same time, the different morphologies all displayed hydrophobicity. Especially, the contact angle of the fibre obtained from organogel in DMF was up to 147°. This research would provide a good pattern for preparation of a special hydrophobic surface through supramolecular self-assembly. 相似文献
10.
Tan G John VT McPherson GL 《Langmuir : the ACS journal of surfaces and colloids》2006,22(17):7416-7420
The system of bis(2-ethylhexyl) sodium sulfosuccinate and 4-chlorophenol, when dissolved in a nonpolar organic solvent, forms an organogel. The fibers of this organogel are formed through a nucleation-growth phenomenon. By reducing evaporation of the pregel solution, the fibers can be directed to grow with extremely long persistence lengths. Alignment of multiple fibers is achieved by inducting growth at the air-solution interface. The interplay of two zones, one above the critical nucleation concentration and the other below, allows orientation to be accomplished as fiber growth proceeds. The observations have implications for the use of the organogel as a template for materials synthesis. 相似文献
11.
Stanley CE Clarke N Anderson KM Elder JA Lenthall JT Steed JW 《Chemical communications (Cambridge, England)》2006,(30):3199-3201
A chiral tris(urea) organogelator gels dmso-water and methanol-water mixtures at low weight percent. The formation of the helical gel fibres is partially inhibited by addition of chloride, which is bound by the gelator, resulting in fully crystalline material characterised by X-ray crystallography. 相似文献
12.
Tiefenbacher K Dube H Ajami D Rebek J 《Chemical communications (Cambridge, England)》2011,47(26):7341-7343
The synthesis of an azo-benzene glycoluril supergelator is reported. The control over the gel/sol state can be accomplished by irradiation and heat, but also (in a unidirectional sense) by incorporation of the glycoluril into a more stable supramolecular assembly. 相似文献
13.
Structural evolution in microbial polyesters 总被引:1,自引:0,他引:1
Heo K Yoon J Jin KS Jin S Sato H Ozaki Y Satkowski MM Noda I Ree M 《The journal of physical chemistry. B》2008,112(15):4571-4582
The crystallization behavior of microbially synthesized poly(3-hydroxybutyrate) (PHB) and its copolymers [P(HB-co-HHx)] containing 2.5, 3.4, and 12 mol % 3-hydroxyhexanoate (HHx) comonomer and the melting of the resultant crystals were studied in detail using time-resolved small-angle X-ray scattering and differential scanning calorimetry. The polyesters were found to undergo primary crystallization as well as secondary crystallization. In the primary crystallization, the thicknesses of the lamellar crystals were sensitive to the crystallization temperature, but no thickening was observed throughout the entire crystallization at a given temperature. The thickness of the lamellar crystals in the PHB homopolymer was always larger than that of the amorphous layers. In the copolymers, by contrast, the randomly distributed HHx comonomer units were found to be excluded from the lamellar crystals into the amorphous regions during the isothermal crystallization process. This interrupted the crystallization of the copolymer chains, resulting in the formation of lamellar crystals with thicknesses smaller than those of the amorphous layers. The lamellar crystals in the copolymers had lower electron densities compared to those formed in the PHB homopolymer. On the other hand, secondary crystallization favorably occurred during the later stage of isothermal crystallization in competition with the continuous primary crystallization, forming secondary crystals in amorphous regions, in particular in the amorphous layers between the primarily formed lamellar crystal stacks. Compared to the primarily formed lamellar crystals, the secondary crystals had short-range-ordered structures of smaller size, a broader size distribution, and a lower electron density. 相似文献
14.
Three new members within the iron tellurate family have been synthesized and characterized by single-crystal diffraction. Fe2Te3O9 is orthorhombic, , , , Z=4, space group Pnma, final agreement factors R1=0.0261(wR2=0.0688) for 1271 independent reflections. Fe3Te4O12 is monoclinic, , , , β=107.950(10)°, Z=4, space group P21/c, final agreement factors R1=0.0380(wR2=0.0281) for 3302 independent reflections. FeTe6O13 is trigonal, , , Z=6, space group , final agreement factors R1=0.0309(wR2=0.0641) for 1264 independent reflections. Together with the four already known members of the family, Fe2TeO5, Fe2TeO6, and Fe2Te3O9 (a dimorphic variant of the afore-mentioned structure with the same chemical formula), and Fe2Te4O11, the iron tellurates now span from relatively Fe-rich and Te-poor to relatively Fe-poor to Te-rich compounds. The structural diversity within Fe-Te-O system is discussed in terms of the lone-pair stereochemistry of the Te4+ anion and the cross-over from Fe3+ to mixed-valence Fe3+/Fe2+ and Fe2+ coordination polyhedra compounds. 相似文献
15.
Polymer-stabilized double emulsions are produced by a two-step process, high shear emulsification in the primary and membrane emulsification in the secondary. By repeated fractionation after each emulsification, we obtain monodisperse double emulsions with the size of the complex droplets ranging from submicrometer to a few micrometers. With osmotic pressure balance between the inner and outer phases, the polymer-stabilized double emulsions remain stable for a year at room temperature without structure deterioration. We generalize laser light scattering to probe the structure and internal dynamics of the complex system by including the effects of the amplitude fluctuations of the scattered fields. Both static light scattering (SLS) and dynamics light scattering (DLS) can resolve the inclusions inside the complex droplets. Water-soluble nonionic surfactants are used to induce destabilization of double emulsions. We find that a double emulsion turns into a simple emulsion within a minute at a surfactant concentration of less than 10(-)(3) mol/L. We demonstrate that DLS is a powerful technique to study the kinetics of destabilization of double emulsions. Coalescence between the internal droplets and the external continuous phase is identified as a major release pathway. 相似文献
16.
Aihua Nie Jinping Wu Chenggang Zhou Shujuan Yao Chen Luo Robert C. Forrey Hansong Cheng 《International journal of quantum chemistry》2007,107(1):219-224
We present a theoretical study of the structural evolution of small minimum energy platinum clusters, using density functional theory (DFT). Three growth pathways were identified. At the subnanoscale, clusters with triangular packing are energetically most favorable. At a cluster size of approximately n = 19, a structural transition from triangular clusters to icosahedral clusters occurs. A less energetically favorable transition from triangular clusters to fcc‐like clusters takes place at around n = 38. Ionization potentials, electron affinities, and magnetic moments of the triangular clusters were also calculated. Understanding the structures and properties will facilitate studies of the chemical reactivity of Pt nanoclusters toward small molecules. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 相似文献
17.
Charles L. Cleveland Uzi Landman Marat N. Shafigullin Peter W. Stephens Robert L. Whetten 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1997,40(1):503-508
The preferred structures of larger gold clusters comprised of 100 to 1000 atoms (1.4–C3.0 nm equivalent diameter) have been determined theoretically via exhaustive search and energy-minimization methods and experimentally by synchrotron x-ray diffraction analysis of purified powder samples of small gold nanocrystals passivated by alkylthiol(ate) self-assembled monolayers. Theory predicts a persistent, close competition, across the entire size-range, among three structure-types: Marks-type decahedral (Dh) structures, monocrystals of a particular (TO+) truncated-octahedral (or ‘Wulffi’) morphology, and symmetrically twin-faulted variants (t-TO+) of the second; all other forms are much less stable. Quantitative comparison of the experimental diffraction patterns with patterns calculated from the structures provides clear evidence for a high abundance of the Dh and t-TO+ forms, but also reveals a definite transition from the former to the latter structures in the 1.7 to 2.0 nm range (~ 200 atoms). Further, the observed (mean) lattice contraction is only about half that predicted, suggesting that the surfactant monolayer acts to reduce the surface energy of the clusters. Taken together, these results suggest that the surfactant monolayer may play a small but important role in differentially stabilizing the higher energy {100}-type facets present to a greater extent in the TO-type structures. 相似文献
18.
Self-assembled graphene organogel (SGO) with 3-dimensional (3D) macrostructure was prepared by solvothermal reduction of a graphene oxide (GO) dispersion in propylene carbonate (PC). This SGO was used as an electrode material for fabricating supercapacitors with a PC electrolyte. The supercapacitor can be operated in a wide voltage range of 0-3 V and exhibits a high specific capacitance of 140 F g(-1) at a discharge current density of 1 A g(-1). Furthermore, it can still keep a specific capacitance of 90 F g(-1) at a high current density of 30 A g(-1). The maximum energy density of the SGO based supercapacitor was tested to be 43.5 Wh kg(-1), and this value is higher than those of the graphene based supercapacitors with aqueous or PC electrolytes reported previously. Furthermore, at a high discharge current density of 30 A g(-1), the energy and power densities of the supercapacitor were measured to be 15.4 Wh kg(-1) and 16,300 W kg(-1), respectively. These results indicate that the supercapacitor has a high specific capacitance and power density, and excellent rate capability. 相似文献
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20.
In this paper, tubular structure has been obtained by self-assembly of cholesterol derivative via sol–gel process. The tube structure and the formation mechanism have been studied and certified by scanning electron microscopy, infrared, ultraviolet-visible spectroscopy (UV–vis) and x-ray diffraction (XRD) data. It is predicated that the tube has been formed by the curl of sheet structure, and the aggregates are composed of two molecules of 1 with H aggregate in laminar structure at micro level. 相似文献