Driving Force for the Association of Amphiphilic Molecules

作者：Mondal Jagannath; Yethiraj Arun^*

来源：Journal of Physical Chemistry Letters, 2011, 2(19): 2391-2395.

DOI：10.1021/jz201046x

The classical view of the hydrophobic effect is that the association of hydrophobic molecules is entropy-driven and caused by the increase in the entropy of water. In this work, we investigate the thermodynamics of association of amphiphilic molecules that consist of a hydrophobic block and a hydrophilic block. Using atomistic simulations, we calculate the potential of mean force between molecules and obtain the entropic and energetic contributions from calculations at two temperatures. For purely hydrophobic molecules, the association is entropy driven, but for the block copolymers the thermodynamic driving force is sensitive to the conditions: The association between block copolymers is energy-driven in pure water and methanol but is entropy-driven in aqueous solutions with high concentrations of added salt. These results demonstrate that the driving force for association in amphiphilic molecules is sensitive to conditions, and the classical view of the hydrophobic effect is not universal.
SECTION: Statistical Mechanics, Thermodynamics, Medium Effects

• 出版日期2011-10-6