Invited Paper BI-WeA1
'Structure' of Water: Myth or Reality?

Wednesday, October 22, 2008, 1:40 pm, Room 202

The “structure” of water at interfaces is a reoccurring interpretation of experimental data or computer simulations employing simplified models for liquid water. Oriented binding of water molecules to a hydrogen bridge bond donor or acceptor group, as observed e.g. in vibrational spectroscopies, does not imply translational symmetry or “structure”, and the orientational order parameter decays typically with the second hydration shell. Whereas the practical significance of surface energy and hence wetability of organic surfaces for adhesion, adhesion failure and biomolecule interaction is obvious, the molecular basis of the hydrophobic and hydrophilic properties of organic surfaces is poorly understood. This is due to the lack of suitable experimental tools for detailed spectroscopy studies of organic interfaces in liquid environments and of molecular detailed theoretical descriptions of hydrophobic/hydrophilic interactions. In this talk I will briefly discuss the limits and potentials of experimental approaches to interfacial water (Neutron Reflectivity, Sum Frequency Generation Spectroscopy, and Terahertz Spectroscopy) to develop a molecular understanding of the properties of water in organic interphases of different surface energy; and time permitting get back to a long standing controversy, the “inert” surface problem, which is a good example for demonstrating the complexity of interfacial water properties.