Long Range Attraction between Glass Surfaces in Cyclohexane-Ethanol Binary Liquids

Abstract

Interaction forces between glass surfaces in cyclohexane-ethanol binary mixtures were investigated using colloidal probe atomic force microscopy. An unusually long range attraction was found in the presence of ethanol in the concentration range of 0.1 ∼ 1.4 mol%. At 0.1 mol% ethanol, the attraction appeared at a distance of 35 ± 3 nm and turned into a repulsive force below 3.5 ± 1.5 nm upon compression. A possible explanation accounting for this long range attraction is the bridging of opposed adsorption layers of ethanol on the glass surfaces.

Macrocluster Formation of Alcohol on Silica Surface in Cyclohexane: Analysis of Interfacial Energy between Adsorption Layer and Bulk Solution

“…The pull-off force also increased to 179 ± 10 mN/m. The shape of this long range interaction force profiles were similar to those observed in ethanol-cyclohexane as well as in 1-propanol-cyclohexane, indicating that the long range attraction was similarly caused by the contact of opposed adsorption layers and the short range repulsion was ascribed to a steric force caused by the overlap of structured layers [20][21][22]. This was confirmed by measuring the adsorption excess amount of methanol onto the glass surfaces [24].…”

“…The spheres and the plates were treated with water vapor plasma (Samco, BP-1, 20 W, 13.56 MHz rf source in 0.6 Torr of argon and water, 50 mL/min flow rate) for 3 min just prior to each experiment in order to ensure the existence of silanol groups on the glass surfaces [29]. After plasma treatment, the cantilever and the glass plate were transferred to a homemade AFM fluid cell [20][21][22], while being kept in purified cyclohexane. The obtained data of force versus sample displacement (extension of piezo tube) profiles were converted to force (F ) versus surface distance (D) profiles following the conventional procedure [28].…”

“…Here, we limited our analysis to the data below 0.09 mol% methanol where the attraction started to decrease in spite of the constant amount of adsorption excess methanol. The decrease in the attraction above 0.09 mol% indicated that the interface might be no longer sharp enough possibly due to the exchange of methanol molecules between the adsorption layers on the surface and those in the bulk solution [20][21][22]34].…”

“…Recently, we have succeeded in identifying the structure of ethanol adsorbed on a silica surface in cyclohexane by employing the combination of surface forces measurement, adsorption excess isotherm measurement and infrared spectroscopy in the attenuated total reflection mode (ATR-FTIR) [20][21][22]. It has been found that ethanol forms a linearly associated polymer extending to ca.…”

Molecular Architecture Studied by the Surface Forces Measurement

“…In order to elucidate them, complementary characterization of the surface and/or interface is necessary. By employing the combination of the surface forces measurement and FT-IR in ATR mode, we have determined the hydrogen-bonded organization of molecules adsorbed on solid surfaces. − In this way, the force measurement (forcemetry) can serve in a role similar to calorimetry.…”