Nanoscale Organization in Aqueous Dicationic Ionic Liquid Solutions

BL Bhargava and ML Klein, JOURNAL OF PHYSICAL CHEMISTRY B, 115, 10439-10446 (2011).

DOI: 10.1021/jp204413n

Coarse-grained molecular dynamics simulations have been performed on aqueous solutions of the gemini dicationic ionic liquid 1,5-bis(3-decylimidazolium-1-yl) pentane bromide at room temperature to study the structure and organization in the solution. Several trajectories corresponding to different concentrations of the ionic liquid (IL) in the solution were generated for about a microsecond. The 40% (w/w) aqueous mixture evolves to a hexagonal structure starting from a random distribution of ions. Spontaneous aggregation of cations was observed in solutions at lower concentrations. Unlike the monocationic ILs, which form spherical aggregates, the aggregates observed in the dicationic IL solution displayed a near-hexagonal arrangement of the hydrophobic cores that were connected to each other by hydrophilic head groups. Anions were found to be present close to the polar head groups. The formation of the interlinked aggregates from a random distribution and the organization at the vapor liquid interface are also discussed.

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