Stratified Dipole‐Arrays Model Accounting for Bulk Properties Specific to Perfluoroalkyl Compounds

Abstract

Perfluoroalkyl compounds are known to exhibit a hydrophobic character on the surface of the material, although the CF bond has a large dipole, which should make the molecular surface polar and hydrophilic. This inconsistency has long been a chemical matter to be solved. Herein, a stratified dipole‐arrays model is proposed: the molecular polar surface can be fully hidden by forming a two‐dimensional aggregate of perfluoroalkyl (Rf) groups; this aggregate is spontaneously induced by dipole–dipole interaction arrays owing to the helical structure of the Rf group. In this model, a ‘short’ Rf group should play the role of a single Rf group with a hydrophilic character, whereas a ‘long’ Rf group should spontaneously form a hexagonal aggregate. To examine this model, Rf‐containing myristic acids with various Rf lengths have been synthesized and their aggregation properties are analyzed by using the Langmuir monolayer technique aided by precise IR spectroscopic analysis.

Perfluorinated Ionomer‐Modified Hole‐Injection Layers: Ultrahigh‐Workfunction but Nonohmic Contacts

“…We attribute this dipole to "gauche" and/or twisted CF 2 CF 2 segments producing a negative-outward directed dipole moment. [ 35 ] To probe the deeper composition profi le in the surface region of these fi lms, we collected core-level X-ray photoemission spectra at both 90° and 30° emission angles. Figure 3 shows the C1s, F1s, O1s, and S2p core-level spectra plotted against binding energies (BEs) referenced to E F and collected at 90° (i.e., perpendicular emission).…”

Helical Inversion of Gel Fibrils by Elongation of Perfluoroalkyl Chains as Studied by Vibrational Circular Dichroism

“…On the other hand, chiral CF8 showed the turbid viscous solution to become a crystal in the same solvent. According to the SDA mode, the length of the perfluoroalkyl chains in CF8 corresponded to one helical turn of a perfluoroalkyl chain . Such a chain readily aggregated to form a closed packed crystalline with hexagonal lattice.…”

“…Recently, extensive work has been performed to develop gelators with perfluoroalkyl chains. A basic concept was formed on the interplay of their dual characters, hydrophobicity and fluorophilicity . From the practical point of view, gelators with perfluoroalkyl chains are a promising application to gelate fluorous solvents .…”

“…A basic concept was formed on the interplay of their dual characters, hydrophobicity and fluorophilicity. [1][2][3][4][5][6][7][8][9][10][11] From the practical point of view, gelators with perfluoroalkyl chains are a promising application to gelate fluorous solvents. 3 In order to develop an efficient gelator, it is of vital importance to clarify the role of perfluoroalkyl chains on gelation ability.…”

Rhodium-Catalyzed (Perfluoroalkyl)olefination of Acetanilides Leading to Perfluoroalkylated Aromatics

“…[20][21][22] Moreover, R F -compounds exhibit unique bulk properties, such as high melting point, low dielectric constant, low solubility in common organic solvents, high chemical stability, and surface hydrophobicity 23) via selfassembly of R F -chains according to the stratified dipole-array model. 24) Therefore, we have been developing novel perfluoroalkylation methodologies, especially utilizing R F -zinc reagents. [25][26][27] Our previous work 25) and work by other research groups [28][29][30][31][32] has provided easy access to (hetero) aromatic compounds directly substituted with an R F -group (Chart 1).…”