title: The effect of the spacer rigidity on the aggregation behavior of two ester-containing Gemini surfactants.
abstract: Two Gemini surfactants with very similar structure but different spacer rigidity, namely 1-dodecanaminium,N,N'-[[(2E)-1,4-dioxo-2-butene-1,4-diyl]bis(oxy-2,1-ethanediyl)]bis[N,N-dimethyl-,bromide] (12-fo-12) and 1-dodecanaminium, N,N'-[(1,4-dioxo-1,4-butanediyl)bis(oxy-2,1-ethanediyl)] bis[N,N-dimethyl-, bromide] (12-su-12), and their monomeric counterpart 1-dodecanaminium, N-[2-(acetyloxy)ethyl]-N,N-dimethyl-, bromide (DTAAB) were synthesized and their aggregation behavior in aqueous solutions was studied by measurements of surface tension, conductivity, isothermal titration calorimetry, dynamic light scattering, and transmission electron microscopy. It was found that the Krafft point of 12-fo-12 was 18.6°C, significantly higher than that of 12-su-12 (7.6°C) and DTAAB (<0°C). The minimum surface areas per surfactant A(min) at the water-air interface of DTAAB, 12-su-12, and 12-fo-12 were determined. It was found that the value of A(min) of DTAAB was larger than half that of 12-su-12 but smaller than half that of 12-fo-12. The values of the degree of association β of the three surfactants were found to be in a sequence of DTAAB>12-su-12>12-fo-12, which was in accord with the sequence of the entropy of micellization. The enthalpies of micellization of the two Gemini surfactants were found to be more negative than double that of DTAAB, and 12-fo-12 had the most negative standard enthalpy of micellization. It was also found that 12-su-12 and DTAAB formed micelles in aqueous solutions, while 12-fo-12 could form micelles and vesicles dependent on the concentration.
authors.affiliation: School of Chemistry and Molecular Engineering, East China University of Science and Technology, Shanghai 200237, China.
authors.forename: Zhiguo
authors.initials: Z
authors.lastname: Zhang
authors.forename: Peizhu
authors.initials: P
authors.lastname: Zheng
authors.forename: Yimin
authors.initials: Y
authors.lastname: Guo
authors.forename: Yan
authors.initials: Y
authors.lastname: Yang
authors.forename: Zhiyun
authors.initials: Z
authors.lastname: Chen
authors.forename: Xiaoyong
authors.initials: X
authors.lastname: Wang
authors.forename: Xueqin
authors.initials: X
authors.lastname: An
authors.forename: Weiguo
authors.initials: W
authors.lastname: Shen
mesh_terms: D000388:Air; D002117:Calcitriol / Q000031:analogs & derivatives* / Q000737:chemistry; D004952:Esters / Q000737:chemistry*; D046529:Microscopy, Electron, Transmission; D010316:Particle Size; D013499:Surface Properties; D013501:Surface-Active Agents / Q000737:chemistry*; D013816:Thermodynamics; D014867:Water / Q000737:chemistry
chemical_list: C411462:1,25-dihydroxy-21-(3-hydroxy-3-methylbutyl)vitamin D(3); D004952:Esters; D013501:Surface-Active Agents; D014867:Water; D002117:Calcitriol