MONOLAYER PROPERTIES OF LONG-CHAIN ALKYLAMMONIUM PERFLUOROHEXANOATES ON THE CONCENTRATED SODIUM-CHLORIDE SOLUTION

Surface pressure (pi)- and surface potential (Delta V)-area (A) isothe rms were obtained for monolayers of alkylammonium perfluorohexanoates of four different alkyl chains (m) on water and 4.4 M NaCl solutions a s a function of molecular area of various temperatures by the Langmuir and the ionizing electrode methods, As for octadecylammonium perfluor ohexanoate (C18F11), the pi-A curves of these long-hydro-short-fluoro chain salt showed three phase transition points, Judging from the surf ace potential and the apparent molar quantity together with our previo us data on the transitions, the first was assigned to the transition f rom the expanded (E) phase to the condensed (C-I) phase, the second fr om the C-I phase to another condensed (C-I') phase, and the third from the (C-I') phase to another condensed (C-II) phase, From the surface potential, the apparent molar entropy change, and the phase diagram, t he orientation of long-hydro-short-fluoro chain salts in the monolayer state was discussed. (C) 1996 Academic Press, Inc.