Physicochemical Nature of Perfluoroalkyl Compounds Induced by Fluorine

Perfluoroalkyl (R_f ) compounds have unique characters represented by a significantly high hydrophobic property, which often makes us consider that R_f groups should be interacted with each other via the 'hydrophobic interaction' as found for a normal hydrocarbon. Due to a similar intuitive and simplistic speculation, the R_f -specific material properties have long been enveloped in darkness for comprehensive understanding, which should lucidly be discussed within a framework of physical chemistry. Here, we show studies on the stratified dipole arrays (SDA) theory, which readily explains the R_f -specific material characters in a comprehensive manner based on only a few fundamental physical parameters of fluorine. The SDA theory encompasses some conventional theories that account for only a part of material properties. In addition, we show that the concept of vibrational spectroscopy of R_f compounds should also be revised, since the mass of fluorine is larger than that of carbon, which is opposite to the hydrocarbon case. In this manner, chemistry of R_f compounds needs another fully revised concept, which cannot be replaced by an extended concept of normal hydrocarbon compounds.