Influence of 1-alkyl-3-methylimidazolium tetrafluoroborate on the lamellar liquid crystal formed by tetraethylene glycol lauryl ether and water

Lyotropic liquid crystals (LLCs) formed in tetraethylene glycol lauryl ether-water system by the addition of 1-alkyl-3-methylimidazolium tetrafluoroborate ([C(n)Mim][BF4], n=2, 4, 6, 8, 10) are characterised by polarised optical microscopy and small-angle X-ray scattering techniques. A small number of [C(n)Mim][BF4] molecules can be solubilised in the liquid crystal without changing the lamellar type. These imidazolium salts are considered as an ideal kind of modifiers for the ordered structure. With different lengths of alkyl chains, [C(n)Mim][BF4] molecules appear in various domains of ordered assemblies: in the water layer for [C(2)Mim][BF4], in the water layer as well as in the polar domain for [C(4)Mim][BF4] and in the apolar domain for the other imidazolium salts with long alkyl chains. Diverse distributions of [C(n)Mim][BF4] molecules in the inner structure bring about their specific influence on the lamellar phase. These results enlighten the use of diverse alkyl-substituted imidazolium salts in modulating LLC and other assemblies and also enrich the aggregation behaviour of these assemblies.