Water–Surfactant Contact Studied by19F–1H Heteronuclear Overhauser Effect Spectroscopy

Intermolecular19F–1H cross-relaxation is measured using heteronuclear Overhauser effect NMR spectroscopy (HOESY) in the micellar solution of cesium pentadecafluorooctanoate. The results are analyzed in terms of a weak1H–19F cross-relaxation between the water protons and the fluorines in the fluoroalkyl chain and a strong19F–19F cross-relaxation within the fluoroalkyl chain. The water–surfactant cross-relaxation indicates a water approach to the first CF2segment in the order of 2.0 Å and a short (⪡ns) water residence time. Evidence of fluorine hydration further inside the micelle is presented.