Water at Hydrophobic Surfaces: Weak Hydrogen Bonding and Strong Orientation Effects

Vibrational studies that selectively probe molecular structure at CCl ₄ /H ₂ O and hydrocarbon/H ₂ O interfaces show that the hydrogen bonding between adjacent water molecules at these interfaces is weak, in contrast to generally accepted models of water next to fluid hydrophobic surfaces that suggest strong hydrogen bonding. However, interactions between these water molecules and the organic phase result in substantial orientation of these weakly hydrogen-bonded water molecules in the interfacial region. The results have important implications for understanding water adjacent to hydrophobic surfaces and the penetration of water into hydrophobic phases.