Department of Chemistry, Faculty of Science, Nara Women's University, Kitauoyanishi-machi, Nara 630-8506, Japan.
Phys Chem Chem Phys. 2019 Dec 7;21(45):25065-25071. doi: 10.1039/c9cp05541j. Epub 2019 Nov 6.
The quaternary-ammonium-salt-type amphiphilic compounds 3Ctris-s-Q X (star-type; carbon number between the central amino and ammonium groups s = 2, 3) and 3Clin-3-Q X (linear-type; carbon number between the hydrophilic groups s = 3), where n represents the alkyl chain length (n = 8, 10, 12, 14) and X represents a counterion [hexafluorophosphate, trifluoromethanesulfonate (OTf), bis(fluorosulfonyl)amide (FSA), and bis(trifluoromethanesulfonyl)amide (NTf)], were synthesized. Except for 3Ctris-3-Q OTf, these trimeric compounds presented melting points lower than 100 °C and therefore are defined as ionic liquids. Among them, 3Ctris-3-Q NTf (n = 8, 12, 14) and 3Clin-3-Q NTf (n = 8, 10) presented melting points lower than 0 °C. The melting points of the amphiphilic trimeric ionic liquids (n = 8, 10), which were lower for the star- than for the linear-type compounds, were higher than those of the corresponding monomeric compounds but lower than those of the corresponding gemini samples. Moreover, the amphiphilic trimeric ionic liquids exhibited higher conductivities and lower viscosities than the corresponding gemini ionic liquids, while the star-type trimeric ionic liquids presented lower conductivities and higher viscosities than those of the linear-type compounds. The amphiphilic trimeric ionic liquids also readily adsorbed at the air/water interface and oriented themselves to form micelles in aqueous solution. This aggregation behavior was not observed in the monomeric and gemini ionic liquids.
季铵盐型两亲性化合物 3Ctris-s-Q X（星型；中心氨基和铵基之间的碳原子数 s = 2,3）和 3Clin-3-Q X（线型；亲水区之间的碳原子数 s = 3），其中 n 代表烷基链长度（n = 8,10,12,14），X 代表抗衡离子[六氟磷酸盐、三氟甲磺酸酯（OTf）、双（氟磺酰基）酰胺（FSA）和双（三氟甲磺酰基）酰胺（NTf）]，被合成出来。除了 3Ctris-3-Q OTf，这些三聚体化合物的熔点都低于 100°C，因此被定义为离子液体。其中，3Ctris-3-Q NTf（n = 8,12,14）和 3Clin-3-Q NTf（n = 8,10）的熔点低于 0°C。两亲性三聚体离子液体（n = 8,10）的熔点比线型化合物的熔点低，它们的熔点高于相应的单体化合物，但低于相应的双子离子液体。此外，与相应的双子离子液体相比，两亲性三聚体离子液体表现出更高的电导率和更低的粘度，而星型三聚体离子液体的电导率比线型化合物的电导率低，粘度比线型化合物的高。两亲性三聚体离子液体也容易在空气/水界面吸附，并在水溶液中定向形成胶束。这种聚集行为在单体和双子离子液体中没有观察到。
