¹⁹F Fast Magic-Angle Spinning NMR Studies of Perfluoroalkanoic Acid Self-Assembled Monolayers

Abstract

The bonding and dynamic properties of perfluoroalkanoic acid self-assembled monolayers (SAMs) on zirconia and titania powders were characterized by Fourier transform infrared and solid-state 19F magic-angle spinning NMR spectroscopy. The perfluoro fatty acids investigated included C(n)F(2n+1)CO2H, n = 7, 13, 15 and 17. The acids bind to both metal oxides via ionic carboxylate bonds, but complete monolayers are only formed on the zirconia. The shift of the CF3 group from -83 ppm in the bulk state to -85 ppm for the adsorbed monolayers is assigned to CF3 groups located at the air/monolayer interface. With the exception of the perfluorooctanoic acid, 19F spin lattice relaxation measurements indicate that the fluorocarbon chains of the adsorbed acids, even in the case of densely packed monolayers, are significantly more mobile than those in the bulk state. The motions associated with the enhanced mobility of the adsorbed acids are proposed to involve reorientations along the long chain axes. No evidence for chain melting in the fluorocarbon SAMs is found for temperatures well above the melting temperature of the bulk acids.

Development of Acoustically Active Nanocones Using the Host–Guest Interaction as a New Histotripsy Agent

“…The spectrum of MCD shows all the above characteristic peaks of BCD. According to the literature, for PFH, the characteristic peaks of CF 2 appear at 1230 and 1150 cm –1 , whereas the characteristic peak of CF 3 appears at 1210 cm –1 . ,− The same characteristic peaks were seen in the FTIR spectrum of PFH as 1235, 1143, and 1199 cm –1 (Figure S6). Although, the peak at 1143 cm –1 was overlapping with the peak of BCD and MCD, clear peaks can be seen at 1242 cm –1 in the spectrum of NCs, indicating the presence of PFH in the cavity, hence providing evidence for the formation of the complex.…”

Photoresponsive Liquid Marbles and Dry Water

“…However, TiO 2 surfaces can be hydrophobized by capping the surface with fatty carboxylic acid or phosphonic acid ligands. 25,26 Perfluorocarbon fatty acids have also been shown to form monolayers on TiO 2 surfaces 28 and are of particular interest because of the oleophobic nature of perfluorocarbon chains.…”

Polyester Preparation in the Presence of Pristine and Phosphonic‐Acid‐Modified Zirconia Nanopowders

“…In addition to the phosphonate group the capping agent PPPA has a carboxylic acid group which is also able to bind to a metal oxide surface. Carboxylates attach mainly in a chelating mode to titania or zirconia surfaces which results in the disappearance of the free acid peak and its replacement by two carboxylate stretching peaks 32–36. In the spectrum of the neat 3‐phosphonopropionic acid the carbonyl signal was observed at 1 720 cm −1 .…”