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Unusual viscosity behavior of a kind of anionic gemini surfactant
Colloids and Surfaces A: Physicochem. Eng. Aspects 308 (2007) 147–149
Brief note
Unusual viscosity behavior of a kind of anionic gemini surfactant Xigang Du a,b , Ling Li a , Yao Lu a,∗ , Zhengyu Yang a a
Technical Institute of Physics and Chemistry, Chinese Academy of Science, Beijing 100080, China b College of Chemical Sciences, Qufu Normal University, Qufu 273165, China Received 8 February 2007; received in revised form 25 April 2007; accepted 11 May 2007 Available online 18 May 2007
Abstract Variations of viscosity of ditetradecyldibenzene disulfonate surfactant Ie solution with concentration and temperature were measured. The results indicated that the Ie solution exhibited high viscosity with increasing of concentration in the absence of added salt at the shear rate of 6 s−1 at 30 ◦ C. The viscosity increased with the increment of temperature at first, then reached a peak and decreased in the end. Additionally, transmission electron microscopy (TEM) was used to visualize the shape of the Ie micelles. The viscosity variation might be attributed to the changes of micelle shapes. © 2007 Elsevier B.V. All rights reserved. Keywords: Anionic gemini surfactant; Viscosity; Micelle
1. Introduction At concentration above the cmc (critical micelle concentration), surfactants tend to self-associate in water to form micelles. The micelles are generally spheroidal at concentration slightly above the cmc [1]. Under appropriate conditions of concentration, salinity, temperature, presence of counterions, etc., spherical micelles can undergo uniaxial growth to form flexible worm-like micelles [1–5]. The most studied micellar solutions are cetyltrimethylammonium bromide (CTAB), cetyltrimethylammonium chloride (CTAC), and cetylpyridinium bromide (CPyB). These systems show a very spectacular viscoelasticity in solution, even in very diluted states, with some aromatic substances added, such as iodophenol and salicylic acid or its sodium salt [6]. The remarkable solution behaviour was explained by the long thread-like and entangled micelles through direct observation of them as substantial images under the electron microscopy [6,7]. Aqueous solutions of some cationic gemini surfactants with short spacer also have a very high viscosity, even in the absence of additives [1,2]. Thus, synthesis of a gemini surfactant with suitable structure is a new way to produce a high viscosity. However, the high viscosity behaviour of anionic gemini surfactants solution without any additive has not been reported. ∗
Corresponding author. E-mail address: [email protected] (Y. Lu).
0927-7757/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.colsurfa.2007.05.020
In our previous work [8], we described the synthesis of seven novel anionic gemini surfactants. In this note, the ditetradecyldibenzene disulfonate surfactant Ie (Fig. 1) solution exhibited high viscosity behaviour. In order to explain the remarkable viscosity with increasing of concentration, transmission electron microscopy (TEM) was used to observe micelle shapes. The variation of viscosity of the Ie solution with temperature was also measured. 2. Experimental 2.1. Rheological measurements The viscosities of the Ie solutions were measured by BrookField DV-III Programmable Rheometer at certain temperature with a maximum deviation of ±0.1 ◦ C controlled by circulationwater bathing establishment. The measurements were performed at the shear rate of 6 s−1 , which were usually used. 2.2. Transmission electron microscopy Staining solution of uranyl acetate (UA) was stocked in 2.0% concentration. Specimens for transmission electron microscopy were prepared by placing a drop of surfactant solution onto a grid coated with Fromvar-carbon film. After removal of excess solution with filter paper, a small amount of staining solution was applied and drained off immediately [6].
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X. Du et al. / Colloids and Surfaces A: Physicochem. Eng. Aspects 308 (2007) 147–149
Fig. 2. Variation of viscosity of the Ie solution with concentration in the absence of added salt at the shear rate of 6 s−1 at 30 ◦ C. Fig. 1. The chemical structure of gemini surfactant Ie.
3. Results and discussion The variation of viscosity of the Ie solution with concentration in the absence of added salt at the shear rate of 6 s−1 at 30 ◦ C was showed in Fig. 2. The viscosities of dilute conventional surfactant solutions without salt were usually slightly greater than that of water. However, Fig. 2 showed that the Ie solution exhibited high viscosity with increasing of concentration in the absence of added salt. The rheological behaviour exhib-
ited by the system was analogous to that observed in solutions of flexible polymers. The phenomenon was also found for the cationic bis-quaternary ammonium gemini surfactant with short spacer [1]. The formation of thread-like micelles and entangled micelles caused the high viscosity of gemini surfactant solutions with increment of their concentrations [2]. In order to explain the remarkable viscosity with increasing of concentration, TEM was used to observe micelle shapes. Micrographs for the Ie solutions of different concentrations were showed in Fig. 3. The micrograph of the 0.01 wt% solution showed (Fig. 3A) many spheroidal micelles represented by the
Fig. 3. TEM images of surfactant Ie solutions: (A) in 0.01 wt% surfactant Ie solution at 30 ◦ C; (B) in 0.2 wt% surfactant Ie solution at 30 ◦ C; (C) in 0.6 wt% surfactant Ie solution at 30 ◦ C; (D) in 0.2 wt% surfactant Ie solution at 65 ◦ C.
X. Du et al. / Colloids and Surfaces A: Physicochem. Eng. Aspects 308 (2007) 147–149
Fig. 4. Viscosity of Ie solution as a function of temperature at 0.2 wt%.
black dots. With increasing of concentration, a lot of thread-like micelles were observed on the micrograph of the 0.2 wt% surfactant solution (Fig. 3B). This was in good agreement with the increase of the viscosity with increment of concentration. The micrograph of the 0.6 wt% solution showed (Fig. 3C) a saturated network (multiconnected or branched threadlike micelles). The viscosity of the Ie solution at the concentration 0.6 wt% was 90 MPa s. It might be easy to ascribe the high viscosity to the saturated network. Fig. 4 illustrated the effect of temperature on the viscosity of Ie solution at 0.2 wt% at the shear rate of 6 s−1 . It was found that the viscosity of the Ie solution depended on temperature greatly. The viscosity of solution increased with the increment of temperature, and there was a peak when temperature reaches about 48 ◦ C. After this point, the viscosity of solution decreased with the increasing of temperature. In the end, the viscosity of solution was almost similar to that of water. These phenomena resembled those in the cationic gemini surfactants system [2] and were explained by the formation and breaking of wormlike micelles. With the increase of temperature, the vesicles or bilayer membrane fragments in the cationic gemini surfactants system will gradually transit into worm-like micelles and at about 50 ◦ C
149
the worm-like micelles take predominance. When the temperature is higher than 50 ◦ C, some worm-like micelles will turn into vesicles or spherical micelles, so the network structure is destroyed and the viscosity decreases with temperature. In the end, viscosity of solution is almost similar to that of solvent when temperature is at about 90 ◦ C. And the micrograph of the 0.2 wt% Ie solution at 65 ◦ C was showed in Fig. 3D. It can be seen from Fig. 3D that worm-like micelles turned into spherical micelles. Thus, the viscosity variation with temperature should be due to the changes of micelle shapes. Although uranyl acetate may perturb the aggregated states of surfactants in dilute solutions, the observed images of electron micrographs were in good agreement with the unusual viscosity behavior. And it is assumed that since the structural changes are observed in all systems at the same uranyl acetate concentration, the observed trends give good indication. 4. Conclusion The anionic gemini surfactant Ie solution exhibited high viscosity at relatively low concentration, even in the absence of added salt, which was only found for some cationic gemini surfactants previously. The high viscosity was explained by the saturated network micelles. In addition, temperature has a great effect on the solution viscosity. And the variation of viscosity with temperature should be due to the transitions of micelle shapes. References [1] [2] [3] [4] [5] [6]
A.B. Groswasser, R. Zana, Y. Talmon, J. Phys. Chem. B 104 (2000) 4005. L.J. Han, H. Chen, P.Y. Luo, Surf. Sci. 564 (2004) 141. T. Imae, R. Kamiya, S. Ikeda, J. Colloid Interface Sci. 108 (1985) 215. Z. Lin, J.J. Cai, L.E. Scriven, H.T. Davis, J. Phys. Chem. 98 (1994) 5984. S.R. Raghavan, E.W. Kaler, Langmuir 17 (2001) 300. Y. Sakaiguchi, T. Shikata, H. Urakami, A. Tamura, H. Hirata, Colloid Polym. Sci. 265 (1987) 750. [7] T. Imae, R. Kamiya, S. Ikeda, J. Colloid Interface Sci. 99 (1984) 3000. [8] X.G. Du, Y. Lu, L. Li, J.B. Wang, Z.Y. Yang, Colloids Surf. A 290 (2006) 132.
Brief note
Unusual viscosity behavior of a kind of anionic gemini surfactant Xigang Du a,b , Ling Li a , Yao Lu a,∗ , Zhengyu Yang a a
Technical Institute of Physics and Chemistry, Chinese Academy of Science, Beijing 100080, China b College of Chemical Sciences, Qufu Normal University, Qufu 273165, China Received 8 February 2007; received in revised form 25 April 2007; accepted 11 May 2007 Available online 18 May 2007
Abstract Variations of viscosity of ditetradecyldibenzene disulfonate surfactant Ie solution with concentration and temperature were measured. The results indicated that the Ie solution exhibited high viscosity with increasing of concentration in the absence of added salt at the shear rate of 6 s−1 at 30 ◦ C. The viscosity increased with the increment of temperature at first, then reached a peak and decreased in the end. Additionally, transmission electron microscopy (TEM) was used to visualize the shape of the Ie micelles. The viscosity variation might be attributed to the changes of micelle shapes. © 2007 Elsevier B.V. All rights reserved. Keywords: Anionic gemini surfactant; Viscosity; Micelle
1. Introduction At concentration above the cmc (critical micelle concentration), surfactants tend to self-associate in water to form micelles. The micelles are generally spheroidal at concentration slightly above the cmc [1]. Under appropriate conditions of concentration, salinity, temperature, presence of counterions, etc., spherical micelles can undergo uniaxial growth to form flexible worm-like micelles [1–5]. The most studied micellar solutions are cetyltrimethylammonium bromide (CTAB), cetyltrimethylammonium chloride (CTAC), and cetylpyridinium bromide (CPyB). These systems show a very spectacular viscoelasticity in solution, even in very diluted states, with some aromatic substances added, such as iodophenol and salicylic acid or its sodium salt [6]. The remarkable solution behaviour was explained by the long thread-like and entangled micelles through direct observation of them as substantial images under the electron microscopy [6,7]. Aqueous solutions of some cationic gemini surfactants with short spacer also have a very high viscosity, even in the absence of additives [1,2]. Thus, synthesis of a gemini surfactant with suitable structure is a new way to produce a high viscosity. However, the high viscosity behaviour of anionic gemini surfactants solution without any additive has not been reported. ∗
Corresponding author. E-mail address: [email protected] (Y. Lu).
0927-7757/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.colsurfa.2007.05.020
In our previous work [8], we described the synthesis of seven novel anionic gemini surfactants. In this note, the ditetradecyldibenzene disulfonate surfactant Ie (Fig. 1) solution exhibited high viscosity behaviour. In order to explain the remarkable viscosity with increasing of concentration, transmission electron microscopy (TEM) was used to observe micelle shapes. The variation of viscosity of the Ie solution with temperature was also measured. 2. Experimental 2.1. Rheological measurements The viscosities of the Ie solutions were measured by BrookField DV-III Programmable Rheometer at certain temperature with a maximum deviation of ±0.1 ◦ C controlled by circulationwater bathing establishment. The measurements were performed at the shear rate of 6 s−1 , which were usually used. 2.2. Transmission electron microscopy Staining solution of uranyl acetate (UA) was stocked in 2.0% concentration. Specimens for transmission electron microscopy were prepared by placing a drop of surfactant solution onto a grid coated with Fromvar-carbon film. After removal of excess solution with filter paper, a small amount of staining solution was applied and drained off immediately [6].
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X. Du et al. / Colloids and Surfaces A: Physicochem. Eng. Aspects 308 (2007) 147–149
Fig. 2. Variation of viscosity of the Ie solution with concentration in the absence of added salt at the shear rate of 6 s−1 at 30 ◦ C. Fig. 1. The chemical structure of gemini surfactant Ie.
3. Results and discussion The variation of viscosity of the Ie solution with concentration in the absence of added salt at the shear rate of 6 s−1 at 30 ◦ C was showed in Fig. 2. The viscosities of dilute conventional surfactant solutions without salt were usually slightly greater than that of water. However, Fig. 2 showed that the Ie solution exhibited high viscosity with increasing of concentration in the absence of added salt. The rheological behaviour exhib-
ited by the system was analogous to that observed in solutions of flexible polymers. The phenomenon was also found for the cationic bis-quaternary ammonium gemini surfactant with short spacer [1]. The formation of thread-like micelles and entangled micelles caused the high viscosity of gemini surfactant solutions with increment of their concentrations [2]. In order to explain the remarkable viscosity with increasing of concentration, TEM was used to observe micelle shapes. Micrographs for the Ie solutions of different concentrations were showed in Fig. 3. The micrograph of the 0.01 wt% solution showed (Fig. 3A) many spheroidal micelles represented by the
Fig. 3. TEM images of surfactant Ie solutions: (A) in 0.01 wt% surfactant Ie solution at 30 ◦ C; (B) in 0.2 wt% surfactant Ie solution at 30 ◦ C; (C) in 0.6 wt% surfactant Ie solution at 30 ◦ C; (D) in 0.2 wt% surfactant Ie solution at 65 ◦ C.
X. Du et al. / Colloids and Surfaces A: Physicochem. Eng. Aspects 308 (2007) 147–149
Fig. 4. Viscosity of Ie solution as a function of temperature at 0.2 wt%.
black dots. With increasing of concentration, a lot of thread-like micelles were observed on the micrograph of the 0.2 wt% surfactant solution (Fig. 3B). This was in good agreement with the increase of the viscosity with increment of concentration. The micrograph of the 0.6 wt% solution showed (Fig. 3C) a saturated network (multiconnected or branched threadlike micelles). The viscosity of the Ie solution at the concentration 0.6 wt% was 90 MPa s. It might be easy to ascribe the high viscosity to the saturated network. Fig. 4 illustrated the effect of temperature on the viscosity of Ie solution at 0.2 wt% at the shear rate of 6 s−1 . It was found that the viscosity of the Ie solution depended on temperature greatly. The viscosity of solution increased with the increment of temperature, and there was a peak when temperature reaches about 48 ◦ C. After this point, the viscosity of solution decreased with the increasing of temperature. In the end, the viscosity of solution was almost similar to that of water. These phenomena resembled those in the cationic gemini surfactants system [2] and were explained by the formation and breaking of wormlike micelles. With the increase of temperature, the vesicles or bilayer membrane fragments in the cationic gemini surfactants system will gradually transit into worm-like micelles and at about 50 ◦ C
149
the worm-like micelles take predominance. When the temperature is higher than 50 ◦ C, some worm-like micelles will turn into vesicles or spherical micelles, so the network structure is destroyed and the viscosity decreases with temperature. In the end, viscosity of solution is almost similar to that of solvent when temperature is at about 90 ◦ C. And the micrograph of the 0.2 wt% Ie solution at 65 ◦ C was showed in Fig. 3D. It can be seen from Fig. 3D that worm-like micelles turned into spherical micelles. Thus, the viscosity variation with temperature should be due to the changes of micelle shapes. Although uranyl acetate may perturb the aggregated states of surfactants in dilute solutions, the observed images of electron micrographs were in good agreement with the unusual viscosity behavior. And it is assumed that since the structural changes are observed in all systems at the same uranyl acetate concentration, the observed trends give good indication. 4. Conclusion The anionic gemini surfactant Ie solution exhibited high viscosity at relatively low concentration, even in the absence of added salt, which was only found for some cationic gemini surfactants previously. The high viscosity was explained by the saturated network micelles. In addition, temperature has a great effect on the solution viscosity. And the variation of viscosity with temperature should be due to the transitions of micelle shapes. References [1] [2] [3] [4] [5] [6]
A.B. Groswasser, R. Zana, Y. Talmon, J. Phys. Chem. B 104 (2000) 4005. L.J. Han, H. Chen, P.Y. Luo, Surf. Sci. 564 (2004) 141. T. Imae, R. Kamiya, S. Ikeda, J. Colloid Interface Sci. 108 (1985) 215. Z. Lin, J.J. Cai, L.E. Scriven, H.T. Davis, J. Phys. Chem. 98 (1994) 5984. S.R. Raghavan, E.W. Kaler, Langmuir 17 (2001) 300. Y. Sakaiguchi, T. Shikata, H. Urakami, A. Tamura, H. Hirata, Colloid Polym. Sci. 265 (1987) 750. [7] T. Imae, R. Kamiya, S. Ikeda, J. Colloid Interface Sci. 99 (1984) 3000. [8] X.G. Du, Y. Lu, L. Li, J.B. Wang, Z.Y. Yang, Colloids Surf. A 290 (2006) 132.