Characterization and solution properties of adamantane-containing quaternary-ammonium-salt-type amphiphilic ionic liquids

Publication date: Available online 20 August 2019Source: Journal of Molecular LiquidsAuthor(s): Risa Kawai, Shiho Yada, Tomokazu YoshimuraAbstractQuaternary-ammonium-salt-type amphiphilic compounds ([CnAdA][X], where n represents the alkyl chain length (n = 1, 2, 4, 6, 8, or 10), X represents a counterion such as [BF4]−, [PF6]−, trifluoromethanesulfonate ([OTf]−), bis(fluorosulfonyl)amide ([FSA]−), or bis(trifluoromethanesulfonyl)amide ([NTf2]−), and Ad and A of AdA represent the adamantane structure and quaternary ammonium group, respectively) were synthesized. The melting points of the prepared compounds were determined by differential scanning calorimetry, and the derivatives with melting points lower than 100 °C were classified as ionic liquids for subsequent analyses. The amphiphilic ionic liquids, [CnAdA][NTf2] (n = 6 and 8), exhibited the lowest melting points (30.6 and 38.7 °C, respectively). Further, the [CnAdA][NTf2] series of amphiphilic ionic liquids exhibited significantly lower conductivities and higher viscosities than the corresponding ionic liquids without the adamantane moiety, [Cn][NTf2]. The viscosities of [CnAdA][NTf2] (n = 6 and 8) decreased significantly with increasing temperature, and showed a larger temperature dependence than that of the viscosities of the [Cn][X] series. The amphiphilic ionic liquids, [C8AdA][X] readily adsorbed at the air/water interface and oriented themselves but did not show the critical micelle conc...
Source: Journal of Molecular Liquids - Category: Molecular Biology Source Type: research