title: Effect of cation symmetry on the organization of ionic liquids near a charged mica surface.
abstract: Atomistic molecular dynamics simulations have been carried out to understand the effect of the symmetry of cations on the microscopic organization of ionic liquids near a charged mica surface. Ionic liquids with a 1,3-alkylimidazolium ([C(n)C(m)im](+)) cation and a bis(trifluoromethylsulfonyl)imide ([NTf2](-)) anion were investigated. Apart from symmetry, the length of the alkyl group attached to the cation is found to crucially determine the ion structure near the solid surface. In the first adsorbed layer, the ring planes of cations with shorter alkyl groups (less than four carbon atoms) are oriented either parallel or perpendicular to the surface. However, cations with longer alkyl tails are exclusively observed to have their ring planes parallel to the mica surface. The alkyl groups too show a similar dependence of their orientation on the tail length. Further, symmetric cations with alkyl groups of intermediate length are more highly structured at the interface than their asymmetric counterparts.
authors.affiliation: Chemistry and Physics of Materials Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore 560 064, India.
authors.forename: Rajdeep Singh
authors.initials: RS
authors.lastname: Payal
authors.forename: Sundaram
authors.initials: S
authors.lastname: Balasubramanian
mesh_terms: D000327:Adsorption; D000538:Aluminum Silicates / Q000737:chemistry*; D002412:Cations / Q000737:chemistry; D003198:Computer Simulation; D052578:Ionic Liquids / Q000737:chemistry*; D008956:Models, Chemical; D008958:Models, Molecular; D055672:Static Electricity
chemical_list: D000538:Aluminum Silicates; D002412:Cations; D052578:Ionic Liquids; C011934:mica