title: Examination of fluorination effect on physical properties of saturated long-chain alcohols by DSC and Langmuir monolayer.
abstract: Partially fluorinated long-chain alcohols have been newly synthesized from a radical reaction, which is followed by a reductive reaction. The fluorinated alcohols have been investigated by differential scanning calorimetry (DSC) and compression isotherms in a Langmuir monolayer state. Their melting points increase with an increase in chain length due to elongation of methylene groups. However, the melting points for the alcohols containing shorter fluorinated moieties are lower than those for the typical hydrogenated fatty alcohols. Using the Langmuir monolayer technique, surface pressure (π)-molecular area (A) and surface potential (ΔV)-A isotherms of monolayers of the fluorinated alcohols have been measured in the temperature range from 281.2 to 303.2K. In addition, a compressibility modulus (Cs(-1)) is calculated from the π-A isotherms. Four kinds of the alcohol monolayers show a phase transition (π(eq)) from a disordered to an ordered state upon lateral compression. The π(eq) values increase linearly with increasing temperatures. A slope of π(eq) against temperature for the alcohols with shorter fluorocarbons is unexpectedly larger than that for the corresponding fatty alcohols. Generally, fluorinated amphiphiles have a greater thermal stability (or resistance), which is a characteristic of highly fluorinated or perfluorinated compounds. Herein, however, the alcohols containing perfluorobutylated and perfluorohexylated chains show the irregular thermal behavior in both the solid and monolayer states.
authors.affiliation: Department of Biophysical Chemistry, Faculty of Pharmaceutical Sciences, Nagasaki International University, 2825-7 Huis Ten Bosch, Sasebo, Nagasaki 859-3298, Japan.
authors.forename: Hiromichi
authors.initials: H
authors.lastname: Nakahara
authors.forename: Shohei
authors.initials: S
authors.lastname: Nakamura
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Okahashi
authors.forename: Daisuke
authors.initials: D
authors.lastname: Kitaguchi
authors.forename: Noritake
authors.initials: N
authors.lastname: Kawabata
authors.forename: Seiichi
authors.initials: S
authors.lastname: Sakamoto
authors.forename: Osamu
authors.initials: O
authors.lastname: Shibata
mesh_terms: D000438:Alcohols / Q000737:chemistry*; D002152:Calorimetry, Differential Scanning; D054879:Halogenation; D013499:Surface Properties; D013696:Temperature
chemical_list: D000438:Alcohols