- Phase behaviors and self-assembly properties of two catanionic surfactant systems: C8F17COOH/TTAOH/H2O and C 8H17COOH/TTAOH/H2O
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Two fatty acids, perfluorononanoic acid (C8F17COOH) and nonanoic acid (C8H17COOH), were mixed with a cationic hydrocarbon surfactant, tetradecyltrimethylammonium hydroxide (TTAOH), in aqueous solutions for comparative investigation. Phase behaviors of the two systems are quite different because of the special properties of the fluorocarbon chains. For the C8H17COOH/TTAOH/H 2O system, a single Lα phase region with phase transition from planar lamellar phase (Lαl phase) to vesicle phase (Lαv phase) was observed. For the C8F 17COOH/TTAOH/H2O system, two single phases consisting of vesicles were obtained at room temperature. One is a high viscoelastic gel phase consisting of vesicles with crystalline state bialyers at the C 8F17COOH-rich side, which was confirmed by freeze-fracture transmission electron microscope (FF-TEM) and differential scanning calorimetry (DSC) measurements. With the increase of TTAOH proportion, another vesicle phase consisting of liquid state bilayers was observed after the two-phase region. The fluorosurfactant systems prefer to form vesicle bilayers than the corresponding hydrocarbon ones because of the rigid structure, the stronger hydrophobicity, and the larger volume of fluorocarbon chains.
- Zhang, Juan,Song, Aixin,Li, Zhibo,Xu, Guiying,Hao, Jingcheng
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- Preparation and characterization of new ionic liquid forms of 2,4-DP herbicide
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In this study, a series of new 2-(2,4-dichlorophenoxy)propionate-based herbicidal ionic liquids (HILs), incorporating well-known, commercially available tetraalkylammonium cations, were synthesized in high yield (≥89%) via a simple two-step procedure. Generally, at room temperature, the products comprising at least one long alkyl substituent in the cation were viscous liquids. All the synthesized salts maintained biological activity against the selected dicotyledonous weeds (common lambsquarters and cornflower). Among the tested salts, the HILs with dodecyltrimethylammonium, trimethyl(tetradecyl)ammonium and trimethyl(octadecyl)ammonium cations were characterized by the highest herbicidal efficacy against both plants. The spray solutions of the prepared HILs revealed their good surface-activation and wetting properties (contact angle = 43–63° and surface tension = 27–29 mN m?1), justifying an enhancement of the biological activity caused by the facilitated penetration of the active substance into the interior of the plant. The values of the octanol–water partition coefficient of the new salts indicate their low potential for bioaccumulation in the soil.
- Niemczak, Micha?,Biedziak, Agnieszka,Czerniak, Kamil,Marcinkowska, Katarzyna
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p. 7315 - 7325
(2017/11/27)
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- Niobium peroxide-catalyzed selective epoxidation of allylic alcohols
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Modified niobium peroxides were prepared and used for catalyzing the epoxidation of allylic alcohols with hydrogen peroxide in the absence of any other solvent under ice bath conditions. Niobium peroxides modified with ionic liquid-type 1-dodecyl- 3-methylimidazolium hydroxide or conventional tetradecyl trimethyl ammonium hydroxide surfactants demonstrated excellent yields (80-99%) for the epoxidation of allylic alcohols to their epoxides even if the reaction was performed without any other solvent at 0°C for 0.5 h. The catalyst characterization demonstrated that the surfactant molecules were anchored on the surface of the niobium catalyst by weak noncovalent interactions. Compared with niobium peroxides, the modified amphiphilic catalysts allowed easier accessibility to hydrophobic substrates and thus demonstrated high reaction rate and excellent recyclability for the epoxidation under mild conditions.
- Chen, Chen,Zhao, Xiuge,Chen, Jizhong,Hua, Li,Zhang, Ran,Guo, Li,Song, Baoning,Gan, Huimei,Hou, Zhenshan
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p. 3231 - 3238
(2015/02/19)
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- Pickering emulsion stabilized by catalytic polyoxometalate nanoparticles: A new effective medium for oxidation reactions
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Decyl-, dodecyl-, and tetradecyltrimethylammonium cations were combined with the catalytic polyoxometalate [PW12O40]3- anion to give spherical and monodisperse nanoparticles that are able to stabilize emulsions in the presence of water and an aromatic solvent. This triphasic liquid/solid/liquid system, based on a catalytic surfactant, is particularly efficient as a reaction medium for epoxidation reactions that involve hydrogen peroxide. The reactions proceed at competitive rates with straightforward separation of the phases by centrifugation. Such catalytic "Pickering" emulsions combine the advantages of heterogeneous catalysis and biphasic catalysis without the drawbacks (e.g., catalyst leaching or separation time). Mixing it up a bit: Spherical nanoparticles of decyl- and dodecyltrimethylammonium cations with [PW12O40] 3- formed stable Pickering emulsions in the presence of an aromatic solvent and water. This system is an efficient medium for epoxidation (see figure). Copyright
- Leclercq, Loic,Mouret, Adrien,Proust, Anna,Schmitt, Veronique,Bauduin, Pierre,Aubry, Jean-Marie,Nardello-Rataj, Veronique
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supporting information
p. 14352 - 14358
(2013/01/15)
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