As the symbol of gemini surfactants, the spacer group connects two surfactant monomers and plays an important role in the self-assembling of gemini surfactants. Recent attention has been paid to the effects of spacer nature and length in aqueous systems. In this study, the aggregation behaviours of quaternary ammonium gemini surfactants 12-s-12 with different spacer length (s = 2, 3, 4, 5, 6, 8, 10, 12) have been investigated in the protic ionic liquid EAN. The micellization behaviour was characterized by surface tension measurement. With the help of small-angle X-ray scattering (SAXS), the size and shape of aggregates were verified. The spacer length effect could be reflected by the changes in the micellization and phase behaviours of 12-s-12/EAN systems. The critical packing parameter of gemini molecules would decrease monotonically with the spacer length, which is supported by SAXS results. Due to the charge screening effect of EAN, the aggregation behaviours of 12-s-12 would be mainly influenced by spacer length. Our results would be the important supplement to the spacer length effect of gemini surfactants in the nonaqueous systems. With the increase of spacer chain length, the reverse hexagonal lyotropic liquid crystal phase would transform into the micellar phase.

中文翻译：

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间隔长度对 EAN 中双子表面活性剂聚集行为的影响

作为双子表面活性剂的标志，间隔基团连接两个表面活性剂单体，在双子表面活性剂的自组装中起重要作用。最近，人们对水性体系中间隔物性质和长度的影响给予了关注。在这项研究中，研究了不同间隔长度（s = 2, 3, 4, 5, 6, 8, 10, 12）的季铵双子表面活性剂12-s-12在质子离子液体EAN中的聚集行为。通过表面张力测量表征胶束化行为。在小角度 X 射线散射 (SAXS) 的帮助下，验证了聚集体的大小和形状。间隔长度效应可以通过 12-s-12/EAN 系统的胶束化和相行为的变化来反映。Gemini 分子的关键堆积参数将随间隔长度单调降低，这得到了 SAXS 结果的支持。由于EAN的电荷屏蔽效应，12-s-12的聚集行为主要受间隔长度的影响。我们的结果将是对非水系统中双子表面活性剂的间隔长度效应的重要补充。随着间隔链长度的增加，反六方溶致液晶相将转变为胶束相。