Synthesis, characterization, and formation of self-assembled monolayers of a phosphonic acid bearing a vinylene-bridged fluoroalkyl chain

An unprecedented phosphonic acid with a vinylene-bridged fluoroalkyl chain (-C6F12-CH=CH-C6F13) was synthesized and characterized. This compound comprises the perfluorohexyl (C6F13) group, which allows the exclusion of the use and formation of bioaccumulative perfluorooctanoic-acid-related compounds (i.e., compounds containing the (C7F15)C moiety). Self-assembled monolayers (SAMs) of the novel phosphonic acid were formed on indium-tin oxide and stainless steel substrates by solution deposition. The surface properties, formation kinetics, and thermal stabilities of the SAMs were investigated by X-ray photoelectron spectroscopy, contact angle measurements, and atomic force microscopy. Compared to the SAMs of known fluorinated phosphonic acids containing CnF2n+1 groups (n = 4, 6, 8), the SAM of this novel phosphonic acid bearing the -C6F12-CH=CH-C6F13 group showed a high uniformity, a lower surface energy, and a lower contact angle hysteresis. In addition, the novel phosphonic acid allowed the rapid modification of metal oxide surfaces and imparted a superior thermal stability compared to conventional fluorinated phosphonic acids. Therefore, this phosphonic acid bearing a vinylene-bridged fluoroalkyl chain is a promising candidate for improving both surface modification and environmental properties in comparison with conventional analogs having long perfluoroalkyl chains.

Automated summary

A novel phosphonic acid with a vinylene-bridged fluoroalkyl chain was synthesized and characterized, showing high uniformity, lower surface energy, and lower contact angle hysteresis on metal oxide surfaces. This compound also allowed for rapid surface modification of metal oxide surfaces and exhibited superior thermal stability compared to traditional fluorinated phosphonic acids.