Perfluoroalkanes remain on water surface even after volatilization: Affinity analysis of fluorinated solvent with water surface

Perfluoroalkyl (Rf) compounds are known to have a poor solubility for most solvents except fluorinated solvents, which is known as a fluorous property. In Langmuir (L) film studies of Rf compounds, fluorinated solvents such as perfluoro-n-alkanes are generally used as a good solvent for depositing a sample monolayer on the water surface. On the other hand, a single Rf chain with a short length such as C6F13- is known to exhibit a totally different character from a condensed matter to have a strong affinity to a water molecule on the water surface via the dipole-dipole interaction, which is known as the dipole interactive (DI) property. On considering the DI property, the solvents of perfluoro-n-alkanes would remain on water for a long time, which may disturb the formation of L film on water. In the present study, details of a liquid layer of perfluoro-n-alkanes on water are investigated by using infrared external reflection (IR ER) spectrometry. Although the perfluoro-n-alkanes are highly volatile, the relevant vibration bands did not disappear even after two hours, which means that they remain on the water surface. Fortunately, however, the remained solvent, C6F14, has been found no disturbing factor for preparation of L films. (c) 2021 Elsevier Inc. All rights reserved.

Automated summary

Perfluoroalkyl (Rf) compounds have poor solubility in most solvents except fluorinated solvents. A single Rf chain with a short length exhibits a strong affinity to water molecules. This study investigates the liquid layer of perfluoro-n-alkanes on water using infrared external reflection spectrometry.