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Surface Adsorption and Aggregation Properties of Novel l ‐Lysine‐Based Gemini Surfactants
Author(s) -
Liang Yaqin,
Hu Zhiyong,
Cao Duanlin
Publication year - 2014
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/s11743-013-1541-6
Subject(s) - chemistry , pulmonary surfactant , adsorption , critical micelle concentration , surface tension , aqueous solution , gibbs isotherm , conductometry , molecule , micelle , nuclear chemistry , inorganic chemistry , organic chemistry , thermodynamics , biochemistry , physics
Abstract Four chiral l ‐lysine‐based gemini surfactants with different spacers were synthesized, namely, disodium (18 R ,23 R )‐12,20,21,29‐tetraoxo‐13,19,22,28‐tetraazatetracontane‐18,23‐dicarboxylate([C 12 ‐2‐C 12 ]Na 2 ), disodium (18 R ,25 R )‐12,20,23,31‐tetraoxo‐13,19,24,30‐tetraazadotetracontane‐18,25‐dicarboxylate([C 12 ‐4‐C 12 ]Na 2 ), disodium(18 R ,27 R )‐12,20,25,33‐tetraoxo‐13,19,26,32‐tetraazatetratetracontane‐18,27‐dicarboxylate([C 12 ‐6‐C 12 ]Na 2 ), disodium(2 R ,2′ R )‐ 2,2′‐(6‐chloro‐1,3,5‐triazine‐2,4‐diyl)bis(azanediyl)bis(6‐dodecanamidohexanoate) ([C 12 ‐T‐C 12 ]Na 2 ). The chemical structures of the prepared compounds were confirmed by 1 H‐NMR, ESI–MS and IR spectra. Further, the critical micelle concentration (CMC) of these surfactants in aqueous solutions was determined by surface tension and conductometry methods at 25 °C. Moreover, the adsorption and micellization behaviors of these surfactants were estimated by pC 20 , the minimum average area per surfactant molecule (A min ), and standard free energy for micellization and adsorption ( Δ G mic∘and Δ G ads∘). The results show that the four gemini surfactants have low CMC values and significantly low surface tension. Furthermore, the surfactants show strong adsorption at the air–water interface. The CMC and A min values of the surfactants were found to be in the order of [C 12 ‐2‐C 12 ]Na 2 < [C 12 ‐4‐C 12 ]Na 2 < [C 12 ‐6‐C 12 ]Na 2 < [C 12 ‐T‐C 12 ]Na 2 , which were in agreement with the sequence of Δ G mic∘and Δ G ads∘. The circular dichroism of the surfactants indicated the formation of chiral aggregates above the CMC values.