Liquid crystalline phases self-organized from a surfactant-like ionic liquid C(16)mimCl in Ethylammonium nitrate

The aggregation behavior of a surfactant-like ionic liquid, 1-hexadecyl-3-methylimidazolium chloride (C(16)mimCl), in a room temperature ionic liquid ethylammonium nitrate (EAN) has been investigated. With increasing C(16)mimCl concentration, a series of ordered aggregates including micelles, normal hexagonal (H(1)), lamellar (L(alpha)), and reverse bicontinuous cubic (V(2)) liquid crystalline (LC) phases can be detected over a large temperature range by using polarized optical microscopy (POM) and small-angle X-ray scattering (SAXS) techniques. When comparing such a phase behavior with that of the C(16)mimCl/H(2)O binary system, an additional V(2) phase is identified and could be attributed to the different affinities of C(16)mimCl to EAN and water. Higher temperatures induce smaller lattice spacing for the LC phases, which may be due to the softening of the solvophobic chains of C(16)mimCl molecules. Both the imidazolium ring structure and alkyl chain of C(16)mimCl molecule are proved to play important roles for the LC phase formation. Dissipative particle dynamic simulations are also carried out at room temperature, and the obtained intuitive three-dimensional (3D) models can help us better understand the self-assembled structures, which are considered to be supplements for the experimental results.