Adsorption of Phytosterol Ethoxylates on Silica in an Aprotic Room-Temperature Ionic Liquid

• Published in: Langmuir Vol. 27; no. 7; pp. 3244 - 3248
• Main Authors: Sakai, Kenichi, Onuma, Yosuke, Torigoe, Kanjiro, Biggs, Simon, Sakai, Hideki, Abe, Masahiko
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 05.04.2011
• Subjects: Chemistry; Exact sciences and technology; General and physical chemistry; Surface physical chemistry; Atomic force microscopy; Binary compound; Force measurement; Non ionic surfactant; Crystals; Ion pair; Surfactant; Silica; Solid; Ionic liquid; Measurement in situ; Imide; Solvation; Adsorption; Phytosterol; Interface; Room temperature; Quartz microbalance
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/la200046k

The adsorption of a nonionic surfactant at a silica/room-temperature ionic liquid interface has been characterized on the basis of analytical data obtained through a combination of surface force measurements, in situ soft-contact atomic force microscope (AFM) images, and quartz crystal microbalance with dissipation monitoring (QCM-D) data. The surfactant employed in this study is a kind of phytosterol ethoxylate (BPS-20), and the ionic liquid selected here is aprotic 1-ethyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide (EmimTFSI). This ionic liquid spontaneously forms solvation layers on silica, being composed of an Emim+ cation layer and EmimTFSI ion pair layers. The addition of BPS-20 disrupts these solvation layers and suggests a surfactant layer adsorbed at the interface. This is the first report demonstrating the adsorption of nonionic surfactants at the solid/aprotic ionic liquid interface.