Dimerization Thermodynamics of Large Hydrophobic Plates: A Scaled Particle Theory Study

The temperature dependence of the association thermodynamics of two large hydrophobic plates has been determined by means of molecular dynamics simulations (Zangi, R.; Berne, B. J. J. Phys. Chem. B 2008, 112, 8634-8644). This offers the opportunity to test the ability of an approach grounded on the basic concept that the reduction in the solvent-excluded volume plays a fundamental role and on a suitable application of scaled particle theory to reproduce such association thermodynamic functions over an extended temperature range. The results indicate that the Gibbs energy change is always largely negative and little dependent oil temperature. The enthalpy change is positive at 0 degrees C, small negative at 25 degrees C, and largely negative at 100 degrees C. The entropy change is largely positive at 0 degrees C, passes through zero at about 85 degrees C, and is negative at 100 degrees C. The strong temperature dependence of the enthalpy and entropy changes, due to a large negative heat capacity change, is almost exactly compensating, so that the Gibbs energy change is little affected. The most part of the present results proves to be in more than qualitative agreement with those obtained by means of molecular dynamics simulations.