Experimental evidence for an original two-dimensional phase structure: An antiparallel semifluorinated monolayer at the air-water interface

Abstract

We show the spontaneous formation of an antiparallel monolayer of diblock semifluorinated n-alkane molecules spread at the air-water interface. We used simultaneous measurements of surface pressure and surface potential versus molecular area and performed grazing x-ray reflectivity experiments to characterize the studied monolayer, which is obtained at almost zero surface pressure and precedes the formation of a bilayer at higher surface pressure. Its thickness, equal to 2.7 nm, was found to be independent of the molecular area. This behavior may be explained by van der Waals and electrostatic interactions.

Single-pass Kelvin force microscopy and dC/dZ measurements in the intermittent contact: applications to polymer materials

“…The F 14 H 20 molecules have a dipole of 3.1 D oriented along the chain at the central –CF 2 –CH 2 -junction. Therefore, macroscopic Kelvin probe studies of Langmuir–Blodgett layers of different F n H m revealed a strong surface potential of −0.8 V [6–7] that is assigned to vertically oriented molecular chains with fluorinated parts facing air. Therefore, the fluoroalkane structures are the useful models for the verification of KFM operations.…”

Size, Shape, and Lateral Correlation of Highly Uniform, Mesoscopic, Self‐Assembled Domains of Fluorocarbon–Hydrocarbon Diblocks at the Air/Water Interface: A GISAXS Study

“…This molecular orientation was also supported by surface potential measurements on Langmuir monolayers, revealing an egative surfacep otential. [12][13][14] However, an antiparallel conformation for FnHm diblocks [15] and the formation of as mecticb ilayer [16] have been proposed, too. Disk-like and striped surface domains were also reportedf or partially fluorinated carboxylic acids [17] and partially fluorinated diether glycerols, [18] respectively.S urfaced omains of variouss hapes were also published for combinations of fluorinated amphiphiles (phosphates, diethyl glycerols) with hydrocarbon and fluorocarbon oils [19] or phospholipids.…”

Multifrequency Atomic Force Microscopy: Compositional Imaging with Electrostatic Force Measurements

“…Kelvin probe studies of Langmuir-Blodgett films of different F n H m~n ϭ 12, 14, m ϭ 8, 12, 20! revealed that the fluoroalkanes' self-assemblies exhibit strong surface potential of Ϫ0.8V~El Abed et al, 2002;Broniatowski et al, 2004!. These results, which are explained by vertical orientation of molecular dipole at the central -CF 2 -CH 2 -junction, serve as a valuable reference for KFM. The KFM and dC/dz data obtained on self-assemblies F 12 H 10 , F 12 H 20 , and F 14 H 20 on different substrates, which are partially described elsewherẽ Alexander et al, 2009;, 2011!…”

“…Kelvin probe studies of Langmuir-Blodgett films of different F n H m ( n = 12, 14, m = 8, 12, 20) revealed that the fluoroalkanes' self-assemblies exhibit strong surface potential of −0.8V (El Abed et al, 2002; Broniatowski et al, 2004). These results, which are explained by vertical orientation of molecular dipole at the central -CF 2 -CH 2 - junction, serve as a valuable reference for KFM.…”