Interfacial film conformation and its molecular arrangement of s-triazine derivatives containing three fluorocarbons without hydrophilic groups

Abstract

A monolayer on the water surface or a Langmuir monolayer of fluorinated long-chain s-triazine derivatives with no hydrophilic groups was formed, and its interfacial conformation was verified. As a highly water-repellent monolayer-forming substance, s-triazine derivatives with fluorocarbon chains of different chain lengths were used. These derivatives were poorly soluble in organic solvents and were spread from a mixed solution of chloroform and trifluoroacetic acid supported by a clean glass rod. Although interaction with the water surface was weak owing to a lack of hydrophilic groups, all the molecules reflected the interfacial film behavior in the surface pressure-area isotherms. These derivatives formed orientation almost perpendicular to the water surface in the normal direction to minimize unstable contact between the water subphase and fluorocarbon in the monolayer on the water surface. Atomic force microscopy revealed that derivatives with long fluorocarbons exhibit a two-dimensional crystal morphology based on van der Waals interactions between fluorocarbons. The multilayers of this derivative were found to form a highly oriented structure by polarized infrared spectroscopy and out-of-plane X-ray diffraction. However, it was predicted that the in-plane molecular packing was not always dense. In addition, the results of the contact angle measurement of the monolayer confirmed a systematic difference based on the change in chain length.