IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Biomaterials Monday Sessions
       Session BI+SS-MoA

Invited Paper BI+SS-MoA6
Computer Simulation of the Behavior of Water near Model Surfaces and Self-Assembled Monolayers

Monday, October 29, 2001, 3:40 pm, Room 102

Session: Role of Water in Biological Systems
Presenter: A.J. Pertsin, Heidelberg Universität, Germany
Authors: A.J. Pertsin, Heidelberg Universität, Germany
T. Hayashi, Heidelberg Universität, Germany
M. Grunze, Heidelberg Universität, Germany
Correspondent: Click to Email
The Grand canonical ensemble Monte Carlo technique is used to simulate the behavior of the TIP4P model of water confined between two parallel hydrophilic or hydrophobic model surfaces and also the surfaces of oligo(ethylene oxide) (EGn) terminated self-assembled monolayers (SAMs). The interaction of water with hydrophobic surfaces is modelled by a conventional (3-9) potential dependent only on the separation of the water oxygen atom from the surface. The model potential for hydrophilic surfaces involves in addition an orientation dependence of the potential well depth, which allows for the orientation of the water hydrogens and lone pairs with respect to the proton-acceptor and/or proton-donor centers on the model surface. The water-SAM interactions are described using an atomistic force field based on ab initio MP2 level results for small EGn-water complexes.@footnote 1@ The transferability of the force field on the particular EGn chains constituting the SAM is tested by comparing the force field predictions with the relevant ab initio DFT results.@footnote 2@ The effect of the surfaces on the contiguous water is analyzed in terms of hydration pressure, average water density, and various distribution functions characterizing the orientational and positional order in water. The simulated water density distribution near the SAM is in good agreement with recent neutron reflectivity measurements which reveal the existence of a fairly thick (c.a. 50 Å) interphase water layer with a noticeably reduced average water density (85-90 % bulk water density).@footnote 3@ @FootnoteText@ @footnote 1@ D. Bedrov, M. Pekny, G. D. Smith, J. Phys. Chem. B 102, 996 (1998). @footnote 2@ R. L. C. Wang, H. J. Kreuzer, M. Grunze, Phys. Chem. Chem. Phys. 2, 3613 (2000). @footnote 3@ D. Schwendel et al., submitted.