Dissymmetric and symmetric anionic gemini surfactants,
N-alkyl-
N’-alkyl-
N,
N’dipropanesulfonylethylenediamine (C
mC
nSul, where
m and
n represent alkyl chain lengths of
m-
n = 4-16, 6-14, 8-12, 10-10, and 12-12), were synthesized by two- or three-step reactions. Their physicochemical properties were characterized by equilibrium surface tension measurements, steady-state fluorescence spectroscopy of pyrene, and dynamic light scattering. The critical micelle concentration (CMC) of the dissymmetric surfactants C
4C
16Sul, C
6C
14Sul, and C
8C
12Sul was slightly lower than that of the symmetric surfactant C
10C
10Sul. The occupied area per molecule (
A) of C
8C
12Sul was smaller than that of C
10C
10Sul, indicating that C
8C
12Sul has a high surface activity. However, the increase in the degree of dissymmetry from C
8C
12Sul to C
6C
14Sul and then to C
4C
16Sul resulted in high surface tension and large
A. Based on the surface tension, the standard free energies of micellization (∆
G°
mic) and adsorption (∆
G°
ads), the efficiency of surface adsorption (p
C20), and the effectiveness of surface adsorption (CMC/
C20) were obtained. These parameters suggested that C
8C
12Sul formed micelles more readily than the other surfactants. The properties determined from the surface tension indicated that C
8C
12Sul’s ability is intermediate between those of C
10C
10Sul and C
12C
12Sul. The pyrene fluorescence and dynamic light scattering results revealed that the micelle size depends on the longer of the two alkyl chains in dissymmetric surfactants.
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