- Ultrasonic Relaxation and Carbon-13 NMR Studies of Dialkylammonium Chloride Micelles
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Ther cmc values of several dialkylmethyl and dialkyldimethylammonium chloride surfactants, with a number of carbon atoms per alkyl chain, nc, between 6 and 12, have been measured by conductivity and ultrasonic absorption techniques.The results agree with earlier cmc measurements for dialkyldimethylammonium chlorides with nc equal to 8, 10, and 12.The aggregation number of dihexylmethylammonium chloride has been determined by 13C NMR.The value of 6 has been found, which is in good agreement with the values obtained for monoalkyl chain surfactants.The kinetic study of the fast exchange process occurring in micellar solutions has been carried out by means of ultrasonic absorption methods on aqueous solutions of dialkylmethylammonium chlorides with 6, 7, and 8 carbon atoms in each alkyl chain.The relaxation time τ1 which characterizes this fast process increases as the alkyl chain length increases as for monoalkyl surfactants.The τ1 values are much closer to those found for straight-chain surfactants with 6, 7, and 8 carbon atoms than those found for straight-chain surfactants with 12, 14, and 16 carbon atoms.The kinetic results are discussed in terms of Aniansson and Wall's theory.
- Lang, Jacques
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- Role of the hydrogen bond donor component for a proper development of novel hydrophobic deep eutectic solvents
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The environmental impact of chemical applications can be reduced by using novel solvents with green properties. In this field, Deep Eutectic Solvents (DESs) are promising liquids thanks to their low toxicity, high eco-compatibility and high easiness and “greenness” of preparation. DESs are mixtures of a hydrogen bond donor molecule (HBD) and a hydrogen bond acceptor molecule (HBA) at the proper molar ratio. In this paper, we present the preparation of novel hydrophobic deep eutectic solvents and the studies of their properties: density, eutectic profiles, ranges of water separation, contamination of the separated phases, extraction capabilities of phenol model polluting molecules, capabilities of extraction at acidic and basic conditions. Interesting results emerged about the role of the components of the DESs because of the use of a properly-chosen set of liquids. Their capabilities were dependent on the nature of the HBD molecule, and in particular on its hydrophobicity. Even the DESs with highly water-soluble HBA showed to be easily separable from water and really efficacious as extracting agents when prepared with hydrophobic HBDs. The results of the extractions of pollutants in acid and basic conditions showed the capability of water separation and extraction efficiency of these mixtures even with water at pH = 2 and pH = 9; therefore, the phenols could interact with these liquids without involvement of any acid/base-type of interactions.
- Tiecco, Matteo,Cappellini, Federico,Nicoletti, Francesco,Del Giacco, Tiziana,Germani, Raimondo,Di Profio, Pietro
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- Powerful tailoring effects of counterions of ammonium surfactants on the phase transitions of solvent-free DNA thermotropic liquid crystals
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Solvent-free DNA-surfactant thermotropic liquid crystals (TLCs) are new developed soft biomaterials in recent years. The phase transition behaviors of these DNA TLCs could be regulated by the chain lengths of used double chain surfactants. While, the impact of counterions of ammonium surfactants on the phase transitions of DNA TLCs is still not clear. Herein, a series of ammonium surfactants with different counterions were prepared and put into use of fabrication of DNA TLCs. With inorganic counterions, the resulted DNA materials exhibit distinct decrease on the thermodynamic stability of LC states along with the size increase of counterions, while, the use of planar p-toluenesulfonate as counterion leads to remarkable increased LC thermostability for the resulted DNA material, due to the different interaction between counterions and surfactant layers. These observations indicate that the LC property of DNA-surfactant complexes could be conveniently tailored by using surfactants with designed counterions, providing a new strategy for designing advanced solvent-free biomaterials.
- Gu, Jingjing,Liu, Han,Luo, Xiliang,Qu, Yang,Wu, Zhongtao,Zhang, Lei
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- The Effects of Single- and Twin-tailed Ionic Surfactants upon Aromatic Nucleophilic Substitution
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Reactions of OH- with 2,4-dinitro-1-chloro-benzene and -naphthalene have been examined in solutions of didodecyldimethylammonium chloride and hydroxide.Rate effects were analysed quantitatively in terms of distribution of reactants between water and the colloidal particles.Second-order rate constants at the surface of the particles are very similar to those in normal aqueous micelles of cetyltrimethylammonium hydroxide, chloride, and bromide and p-octyloxybenzyltrimethylammonium bromide and are slightly higher than in water.Similar observations were made on the reaction of OH- with 2,4-dinitro-1-fluorobenzene.
- Cipiciani, Antonio,Germani, Raimondo,Savelli, Gianfranco,Bunton, Clifford A.,Mhala, Marutirao,Moffatt, John R.
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p. 541 - 546
(2007/10/02)
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- Process for preparing 2,2'-azobis(2,4-dimethyl-4-methoxypentanenitrile)
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A process for the preparation of 2,2'-azobis(2,4-dimethyl-4-methoxypentanenitrile) in improved yields with improved filtering characteristics, said process comprising reacting 2-amino-2,4-dimethyl-4-methoxypentanenitrile with a metal hypochlorite in the presence of water, a quaternary ammonium surface active compound and ionic bromide wherein the equivalent ratio of ionic bromide to surface active compound is 0.4:1-4:1 at a temperature of about -10° C. to about 30° C., and recovering 2,2'-azobis(2,4-dimethyl-4-methoxypentanenitrile) from the reaction mixture.
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