Fluorocarbon Surfactant/Water Mesomorphic Phases: Part 3—XH and 2H Pulsed n.m.r. Study of Water in the Lamellar Phase of Ammonium Perfluoro-octanoate

Abstract

Proton and deuteron relaxation times have been measured for water in the lamellar phase of the ammonium perufloro-octanoate + water system. Changes in T1 and T2 with variation of temperature and composition have been determined. Water proton T2 values indicate the presence of a proton exchange reaction between water and ammonium ions with k≃ 102–103 s–1. Most of the water molecules and ammonium ions have motions similar to those of normal liquids. A fraction of water molecules is bound to the fluorocarbon surfactant head groups via hydrogen bonds. The rotational correlation time of these bound molecules is of the order of 10–9 s and an upper limit of 10–6–10–7 s can be placed on the life-time of the surface-water hydrogen bonds.