| Three ether-type imidazoliun ionic liquid surfactants CnOCminCl with different alkyl chains(3-decyloxy methyl-1-methyl-1H-imidazol-3-ium chloride,3-dodecyloxymethyl-1-methyl-1H-imidazol-3-ium chloride and3-tetradecyloxy methyl-1-methyl-1H-imidazol-3-iumchloride) have been synthesized involving two steps and characterized by NMR.The critical micelle concentration of the surfactants aqueous solution has been measured in thetemperature range from20℃to50℃by the measurements on conductivity. The critical micelleconcentrations also obtained through the surface tension and fluorescence measurements at25℃.It can beseen the values were reliable. A series of useful parameters like critical micelle concentration (CMC),surface tension at the cmc (γcmc), the degree of counterion association of micelle (β)，adsorption effciency(pC20) have been determined from the measurements obtained by surface tension and conductivity method.The results reveal that the value of the CMC decreased, the degree of counterion association of micelle (β)and the conductivity decreased, the surface tension at CMC increased with increasing hydrophobic alkylchain length.The critical micelle concentration increased and the degree of counterion association ofmicelle (β) reduced with increasing the temperature. Through the thermodynamic parameters (ΔG, ΔH andΔS) obtained by use of phase separation model, we found that the micellization process was spontaneousprocess. In the investigated temperature range, the enthalpy-entropy compensation effect can be observedand the entropy (ΔH) was the dominant factor responsible in the process of micellization, it is anentropy-driven process. Analysis of thermal stability measurement indicated that the thermal stability ofthese long chain imidazoliniums increase with an increase in chain length.The lyotropic liquid crystal (LLC) composed of surfactants CnOCminCl and water are investigated byusing polarized optical microscopy (POM) and2H NMR spectroscopy. In addition, with the help of fouriertransform infrared spectra (FTIR), the formation mechanism of CnOCminCl/water system are discussed indetails. It is found that alkyl chain length and the concentration of surfactants affect the structures of phases.The influence of temperature (at constant surfactant concentration)was also investigated for somesurfactant solutions. The results showed that the liquid crystalline structure is stable. The phases transfer process is not completely identical for different chain lengths imidazolium amphiphilesThe results showsthat the formation of such phases is considered as a synergetic result of the H-bond network.Ten kinds of organic solvents, including methanol, ethanol,1-propanol, ethylene glycol,have beenselected to study the influence of organic additives on CMC and degree of counter ion binding, β, ofC14OCminCl in water by conductivity. The micellization of C14OCminCl in these water-alcohol mediahave been found to be both dependent on nature as well as the concentration of alcohol in water. The CMCvalues shift toward higher concentration with increase in alcoholic content up to certain concentrationbeyond which decrease in CMC is registered in case of all the alcohols. However, the maximum in theCMC versus concentration of alcohol shifts to lower concentration with the increase in number of carbonsin alcohol β shows the inverse peaked behaviour in conformity with the CMC variation. In this paper, theviscosity of the mixtures of NaCl/C14OCminCl/Alcohol in aqueous was measured and the effect of shortchain alcohols on the self-assembly of surfactants in solutions was studied. The alcohols of methanol,ethanol,1-propanol have little effect on the viscosity of0.1M C14OCminCl solution without NaCl addition.While in the presence of NaCl viscosity first increases with ethylene glycol addition up to a certainconcentration and then decreases. |
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