Preparation of the Langmuir Monolayer of Polytetrafluoroethylene by Spreading from Solid Tablets

In this study, we unprecedentedly fabricated a Langmuir monolayer of polytetrafluoroethylene (PTFE) using a novel method. The prevailing opinion is that it is impossible for a completely insoluble substance, such as PTFE, to form monolayers on the water surface/Langmuir monolayers, owing to limitations in the preparation method. A solid tablet was prepared using PTFE and floated on the water surface for a day and night to detect the surface pressure. When two-dimensional compression was applied, a surface pressure-area isotherm was obtained, suggesting the formation of a Langmuir monolayer. Upon transfer to a solid substrate, an X-ray photoelectron spectrum derived from fluorine atoms was obtained, and an atomic force microscope image of the thickness of a single fluorocarbon chain was obtained. When the water contact angle of the monolayer on the solid substrate was measured, a value equivalent to that of PTFE in a three-dimensional solid state was obtained. Thus, this study is the first to produce a monolayer and Langmuir-Blodgett film of insoluble PTFE on a water surface. Because the C-F bonds in the fluorocarbon chains are inherently polarized, we predicted that the PTFE molecules would be more stable on the water surface when liberating and interacting with water than through intermolecular interactions in a solid tablet.