Li Yajuan, Li Peixun, Dong Chuchuan, Wang Xiaoyong, Wang Yilin, Yan Haike, Thomas Robert K
Key Laboratory of Colloid and Interface Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, People's Republic of China.
Langmuir. 2006 Jan 3;22(1):42-5. doi: 10.1021/la051544n.
The aggregation properties of cationic gemini surfactants alkanediyl-alpha,omega-bis(dodecyldimethylammonium bromide), [C(12)H(25)(CH(3))(2)N(CH(2))(m)(CF(2))(n)(CH(2))(m))N(CH(3))(2)C(12)H(25)]Br(2) [where 2m + n = 12 and n = 0, 4, and 6; designated as 12-12-12, 12-12(C(4)(F))-12, and 12-12(C(6)(F))-12, respectively] have been studied by microcalorimetry, time-resolved fluorescence quenching, and electrical conductivity. Compared with a fully hydrocarbon spacer of 12-12-12, the fluorinated spacer with a lower ratio of CF(2) to CH(2) in 12-12(C(4)(F))-12 tends to disfavor the aggregation, leading to larger critical micelle concentration (cmc), lower micelle aggregation number (N), and less negative Gibbs free energy of micellization (DeltaG(mic)). However, the fluorinated spacer with a higher ratio of CF(2) to CH(2) in 12-12(C(6)(F))-12 may prompt the aggregation, resulting in lower cmc, higher N, and more negative DeltaG(mic). It is also noted that enthalpy change of micellization (DeltaH(mic)) for 12-12(C(4)(F))-12 is the most exothermic, but the values of DeltaH(mic) for 12-12-12 and 12-12(C(6)(F))-12 are almost the same. These results are rationalized in terms of competition among the enhanced hydrophobicity and the rigidity of the fluorinated spacer, and the variation of immiscibility of the fluorinated spacer with the hydrocarbon side chains.
通过微量量热法、时间分辨荧光猝灭法和电导率法研究了阳离子双子表面活性剂链烷二基-α,ω-双（十二烷基二甲基溴化铵），[C(12)H(25)(CH(3))(2)N(CH(2))(m)(CF(2))(n)(CH(2))(m))N(CH(3))(2)C(12)H(25)]Br(2) [其中2m + n = 12且n = 0、4和6；分别指定为12-12-12、12-12(C(4)(F))-12和12-12(C(6)(F))-12]的聚集性质。与12-12-12的全烃间隔基相比，12-12(C(4)(F))-12中CF(2)与CH(2)比例较低的氟化间隔基倾向于不利于聚集，导致更大的临界胶束浓度（cmc）、更低的胶束聚集数（N）和更小的胶束化吉布斯自由能负值（ΔG(mic)）。然而，12-12(C(6)(F))-12中CF(2)与CH(2)比例较高的氟化间隔基可能会促进聚集，导致更低的cmc、更高的N和更负的ΔG(mic)。还注意到12-12(C(4)(F))-12的胶束化焓变（ΔH(mic)）是放热最多的，但12-12-12和12-12(C(6)(F))-12的ΔH(mic)值几乎相同。根据氟化间隔基增强的疏水性和刚性以及氟化间隔基与烃侧链不混溶性的变化之间的竞争，对这些结果进行了合理的解释。
