摘要
Abstract We report on the rheological behavior of wormlike micelles constructed by ionic liquid surfactant [Csmim]Br （1-octyl-3-methylimidazolium bromide） and anionic surfactant sodium oleate （NaOA） in aqueous solution. The effects of surfactant composition, total surfactant concentration, added salts, and temperature were investigated. The prevailing surfactant effect at lower concentration and the leading cosolvent effect at higher concentration of [Csmim]Br may be the main reasons for appearance of well-established maximum in key rheologi- cal parameters with variation of surfactant composition and total surfactant concentration. The Cole-Cole plots demon- strate that the systems （total surfactant concentration falls within 0.17-0.35 mol. L- 1 and molar ratio 0.33≤R ≤ 0.50） fit the Maxwell＇s mechanical model as linear viscoelastic fluid. The addition of NaBr or sodium salicylate decreases significantly the viscosity and the relaxation time of the wormlike micelle solution but cannot change the value of plateau modulus Go. The present system has low rheological tolerance to temperature. The increase of temperature decreases the average contour length and viscosity of wormlike micelles and thus strengthens the relaxation progress of diffusion and weakens the relaxation progress of reptation. Increasing the temperature also decreases the value of plateau modulus G0 and shifts the minimum value of the loss modulus G″min to higher frequencies.
Abstract We report on the rheological behavior of wormlike micelles constructed by ionic liquid surfactant [Csmim]Br （1-octyl-3-methylimidazolium bromide） and anionic surfactant sodium oleate （NaOA） in aqueous solution. The effects of surfactant composition, total surfactant concentration, added salts, and temperature were investigated. The prevailing surfactant effect at lower concentration and the leading cosolvent effect at higher concentration of [Csmim]Br may be the main reasons for appearance of well-established maximum in key rheologi- cal parameters with variation of surfactant composition and total surfactant concentration. The Cole-Cole plots demon- strate that the systems （total surfactant concentration falls within 0.17-0.35 mol. L- 1 and molar ratio 0.33≤R ≤ 0.50） fit the Maxwell＇s mechanical model as linear viscoelastic fluid. The addition of NaBr or sodium salicylate decreases significantly the viscosity and the relaxation time of the wormlike micelle solution but cannot change the value of plateau modulus Go. The present system has low rheological tolerance to temperature. The increase of temperature decreases the average contour length and viscosity of wormlike micelles and thus strengthens the relaxation progress of diffusion and weakens the relaxation progress of reptation. Increasing the temperature also decreases the value of plateau modulus G0 and shifts the minimum value of the loss modulus G″min to higher frequencies.
基金
This work is supported by the National Natural Science Foundation of China （Grant Nos. 21173079, 91334203 and 21476072）, the 111 Project （No. B08021） and the Fundamental Research Funds for the central universities of China.
