title: Influence of Nanosegregation on the Surface Tension of Fluorinated Ionic Liquids.
abstract: We have investigated, both theoretically and experimentally, the balance between the presence of alkyl and perfluoroalkyl side chains on the surface organization and surface tension of fluorinated ionic liquids (FILs). A series of ionic liquids (ILs) composed of 1-alkyl-3-methylimidazolium cations ([CnC1im] with n = 2, 4, 6, 8, 10, or 12) combined with the perfluorobutanesulfonate anion was used. The surface tensions of the investigated liquid salts are considerably lower than those reported for non-fluorinated ionic liquids. The most surprising and striking feature is the identification, for the first time, of a minimum at n = 8 in the surface tension versus the length of the IL cation alkyl side chain. Supported by molecular dynamics (MD) simulations, it was found that this trend is a result of the competition between the two nonpolar domains (perfluorinated and aliphatic) pointing toward the gas-liquid interface, a phenomenon which occurs in ILs with perfluorinated anions. Furthermore, these ILs present the lowest surface entropy reported to date.
authors.affiliation: Department of Chemistry, CICECO-Aveiro Institute of Materials, University of Aveiro , 3810-193 Aveiro, Portugal.
authors.forename: Andreia
authors.initials: A
authors.lastname: Luís
authors.affiliation: Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa , 1049 001 Lisboa, Portugal.
authors.forename: Karina
authors.initials: K
authors.lastname: Shimizu
authors.affiliation: Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa , 2780-157 Oeiras, Portugal.
authors.forename: João M M
authors.initials: JM
authors.lastname: Araújo
authors.affiliation: Department of Chemistry, CICECO-Aveiro Institute of Materials, University of Aveiro , 3810-193 Aveiro, Portugal.
authors.forename: Pedro J
authors.initials: PJ
authors.lastname: Carvalho
authors.affiliation: QOPNA Unit, Department of Chemistry, University of Aveiro , 3810-193 Aveiro, Portugal.
authors.forename: José A
authors.initials: JA
authors.lastname: Lopes-da-Silva
authors.affiliation: Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa , 1049 001 Lisboa, Portugal.
authors.forename: José N
authors.initials: JN
authors.lastname: Canongia Lopes
authors.affiliation: Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa , 2780-157 Oeiras, Portugal.
authors.forename: Luís Paulo N
authors.initials: LP
authors.lastname: Rebelo
authors.affiliation: Department of Chemistry, CICECO-Aveiro Institute of Materials, University of Aveiro , 3810-193 Aveiro, Portugal.
authors.forename: João A P
authors.initials: JA
authors.lastname: Coutinho
authors.affiliation: Department of Chemistry, CICECO-Aveiro Institute of Materials, University of Aveiro , 3810-193 Aveiro, Portugal.
authors.forename: Mara G
authors.initials: MG
authors.lastname: Freire
authors.affiliation: Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa , 2780-157 Oeiras, Portugal.
authors.forename: Ana B
authors.initials: AB
authors.lastname: Pereiro