Grid-based dynamic electronic publication: A case study using combined experiment and simulation studies of crown ethers at the air/water interface.
Esther R Rousay, Hongchen Fu, Jamie M Robinson, Jeremy G Frey, Jonathan W Essex
School of Chemistry, University of Southampton,
Highfield, Southampton, SO17 1BJ, UK

Abstract The Publication@Source Paradigm and Challenges Body Molecular Dynamics Simulations Comparisons and Conclusions Acknowledgements Appendix:The TriScapeRDF browser References Glossary Search
Case Study Crown ether molecules at the water/air interface Introduction Benzo-15-Crown-5 UV Spectrum of Benzo-15-Crown-5 Surface Tension Measurements Second Harmonic Generation SHG Isotherm SHG Isotherm .2 Polarisation Dependence Polarisation Dependance Analysis The molecular hyperpolarisability and molecular orientation The molecular hyperpolarisability and molecular orientation .2 Analysis

SHG Isotherm .2

An equally good fit can be obtained with φ = 0; the experimental results are not sufficiently sensitive to determine the phase accurately. The free energy of adsorption for the benzocrown at the air/water interface is then obtained from K=1/55.5exp(-ΔabsG0/RT), where 55.5 is the molarity of bulk water; the value are shown in table 1.

? φ=90o φ = 0o
K/M-1 2162?70 816?65
ΔGads/kJ mol-1 -28.7?0.1 -26.3?0.1

Table 1 The Langmuir adsorption equilibrium constant and the adsorption free energy for two different assumptions of the phase difference between the SHG fields from the crown ether and the bare air/water interface.

The difference between the isotherm determined by SHG and the surface excess from surface tension is puzzling. We therefore investigated if changes in the orientation of the crown ether with concentration could be the cause of this difference.

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