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A Comprehensive Study on the Synthesis and Micellization of Disymmetric Gemini Imidazolium Surfactants
Author(s) -
Zhao Xiaohui,
An Dong,
Ye Zhiwen
Publication year - 2016
Publication title -
journal of surfactants and detergents
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.349
H-Index - 48
eISSN - 1558-9293
pISSN - 1097-3958
DOI - 10.1007/s11743-016-1830-y
Subject(s) - chemistry , surface tension , pulmonary surfactant , critical micelle concentration , thermodynamics of micellization , analytical chemistry (journal) , adsorption , fluorescence , conductivity , aggregation number , aqueous solution , micelle , thermodynamics , organic chemistry , biochemistry , physics , quantum mechanics
Two groups of disymmetric Gemini imidazolium surfactants, [C 14 C 4 C m im]Br 2 ( m = 10, 12, 14) and [C m C 4 C n im]Br 2 ( m + n = 24, m = 12, 14, 16, 18) surfactants, were synthesized and their structures were confirmed by 1 H NMR and ESI–MS spectroscopy. Their adsorption at the air/water interface, thermodynamic parameters and aggregation behavior were explored by means of surface tension, electrical conductivity and steady‐state fluorescence. A series of surface activity parameters, including cmc, γ cmc , π cmc , p C 20 , cmc/ C 20 , Γ max and A min , were obtained from surface tension measurements. The results revealed that the overall hydrophobic chain length ( N c ) for [C 14 C 4 C m im]Br 2 and the disymmetry ( m/n ) for [C m C 4 C n im]Br 2 had a significant effect on the surface activity. The cmc values decreased with an increase of N c or m/n . The thermodynamic parameters of micellization (Δ G m θ , Δ H m θ , Δ S m θ ) derived from the electrical conductivity indicated that the micellization process of [C 14 C 4 C m im]Br 2 and [C m C 4 C n im]Br 2 was entropy‐driven at different temperatures, but the contribution of Δ H m θ to Δ G m θ was enhanced by increasing N c or m/n . The micropolarity and micellar aggregation number ( N agg ) were estimated by steady‐state fluorescence measurements. The results showed that the surfactant with higher N c or m/n can form larger micelles, due to a tighter micellar structure.