Viscosity measurements have been made to the solutions of dodecyltrimethylammonium bromide (DTAB) and cetyltrimethylammonium bromide (CTAB) in 0.10, 0.20, 0.30, and 0.40 volume fractions of methanol in methanol-water mixed solvent media at 298.15, 308.15, 318.15, and 323.25 K. Critical micelle concentration (CMC) values have been determined. From relative viscosity for surfactant solutions, related viscosity
Cationic surfactants find applications on different fields such as antibacterial properties, lubricants, retarding agents, softeners, and antistatic agents [
Study of viscosity is very important to elucidate the behavior of solute-solvent interaction [
Two cationic surfactants were used for the investigation: dodecyltrimethylammonium bromide (DTAB) and cetyltrimethylammonium bromide (CTAB). These chemicals were purchased from Loba Chemie Private Limited, Mumbai, India, whereas methanol was purchased from Merck, India.
Doubly distilled water was used for all experiments and the solvent mixtures of desired composition were prepared by mixing water and methanol volumetrically in volumetric flask maintained at constant temperature in water bath. The solvent mixture was kept overnight to ensure the proper mixing of the water and alcohol. Accurate weight of surfactant with the help of digital high precision electronic balance (accuracy
Viscosities of solutions were calculated by viscous flow time (VFT) method using the Mansingh Survismeter [
When methanol is added in water, it mixes rapidly and the mixing is exothermic due to which there is considerable reduce in volume. The decrease in volume may be due to breaking of “iceberg” structure of water. In spite of this, there is decrease in the dielectric constant and increase in viscosity when methanol is added in water. The physical properties such as density (
Properties of methanol-water mixtures containing (0.10, 0.20, 0.30, and 0.40) volume fraction of methanol at 298.15 K, 308.15 K, 318.15 K, and 323.15 K.
Volume fraction of methanol |
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0.10 | 298.15 | 0.98297 | 1084.4 | 75.09 |
308.15 | 0.97973 | 866.5 | 71.57 | |
318.15 | 0.97604 | 701.7 | 68.18 | |
323.15 | 0.97438 | 637.5 | 66.45 | |
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0.20 | 298.15 | 0.96963 | 1310.6 | 71.61 |
308.15 | 0.96632 | 1021.7 | 68.14 | |
318.15 | 0.96162 | 807.5 | 64.80 | |
323.15 | 0.95875 | 730.0 | 63.15 | |
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0.30 | 298.15 | 0.95620 | 1471.2 | 67.65 |
308.15 | 0.95160 | 1141.8 | 64.25 | |
318.15 | 0.94626 | 895.7 | 60.99 | |
323.15 | 0.94331 | 805.2 | 59.41 | |
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0.40 | 298.15 | 0.93957 | 1447.5 | 63.53 |
308.15 | 0.93364 | 1203.4 | 60.34 | |
318.15 | 0.93140 | 930.9 | 57.18 | |
323.15 | 0.92800 | 828.8 | 55.62 |
The variation of viscosity with concentration of solutions of DTAB and CTAB is presented in Figures
CMC values of dodecyltrimethylammonium bromide (DTAB) and cetyltrimethylammonium bromide (CTAB) in water and 0.10, 0.20, 0.30, and 0.40 volume fractions of methanol-water at 298.15 K, 308.15 K, 318.15 K, and 323.15 K.
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Volume fraction of methanol | CMC/mM | |
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DTAB | CTAB | ||
298.15 | 0.0 | 14.5 | 0.97 |
0.1 | 17.5 | 1.21 | |
0.2 | 20.5 | 1.76 | |
0.3 | 25.1 | 3.86 | |
0.4 | 34.5 | 6.83 | |
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308.15 | 0.0 | 15.4 | 1.12 |
0.1 | 18.1 | 1.38 | |
0.2 | 21.7 | 1.80 | |
0.3 | 26.4 | 4.56 | |
0.4 | 35.6 | 7.23 | |
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318.15 | 0.0 | 16.3 | 1.23 |
0.1 | 19.5 | 1.68 | |
0.2 | 22.8 | 2.64 | |
0.3 | 27.3 | 5.74 | |
0.4 | 36.7 | 7.47 | |
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323.15 | 0.0 | 17.3 | 1.30 |
0.1 | 20.5 | 1.80 | |
0.2 | 23.7 | 2.83 | |
0.3 | 28.1 | 5.82 | |
0.4 | 37.8 | 7.44 |
Viscosity versus surfactant concentration plot for DTAB in water at 298.15 K.
Viscosity versus surfactant concentration plot for CTAB in water at 308.15 K.
From Figures
Viscosity versus concentration of DTAB solution at 298.15 K.
Viscosity versus concentration of CTAB solution at 298.15 K.
The graphical presentation of CMC with volume fraction of methanol of DTAB and CTAB at different temperatures are given in Figures
Variation of CMC with volume fraction of methanol of DTAB solution at different temperatures.
Variation of CMC with volume fraction of methanol of CTAB solution at different temperatures.
The interaction between solute and solvent is well described in terms of viscosity
Plot of
Plot of
Plot of
Variation of viscosity
Variation of viscosity
It is seen from Figures
The influence of methanol addition on micellization of DTAB and CTAB has been investigated by viscosity measurement. CMC values are determined in 0.10, 0.20, 0.30, and 0.40 volume fractions of methanol-water mixed solvent media at 298.15 K, 308.15 K, 318.15 K, and 323.15 K. These values of CMC reveal that CMC increases with the increase volume fraction of methanol-water due to decrease in dielectric constant of medium as well as due to breaking of water structure. Moreover, calculation of viscosity
The authors declare that there are no competing interests regarding the publication of this paper.
One of the authors, Sujit Kumar Shah, would like to acknowledge the University Grants Commission, Nepal for the Ph.D. fellowship.