Hydrophobic hydration is widely understood to provide a driving force for biological membrane formation and protein folding, and yet many fundamental questions regarding the structure of water at hydrophobic interfaces remain unanswered.  Early studies of hydrophobic hydration envisioned the formation of a �microscopic iceberg� or �chlathrate-like� structures around non-polar solutes. Although both computer simulations and neutron scattering measurements fail to reveal such rigid structures, time resolved infrared pump-probe and nmr experiments, as well as H-bond jump theories, indicate that water molecules rotate more slowly at hydrophobic interfaces than in bulk water (under ambient conditions). Here we provide experimental evidence, obtained by combining Raman spectroscopy and multivariate curve resolution (Raman-MCR), which reveals the depletion of weak water-water hydrogen bonds and the enhanced ordering of stronger hydrogen bonds around hydrophobic solutes.  Moreover, we find that these changes in hydrophobic water structure are enhanced at low temperature and disappear at high temperature, over the ambient liquid temperature range of water.

Water H-bond strength changes in hydrophobic hydration shells

243rd National Meeting (2012)

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