Driving force for hydrophobic interaction at different length scales

Area of Science:

• Physical Chemistry
• Materials Science
• Computational Chemistry

Background:

• Hydrophobic interactions are crucial in various chemical and biological processes.
• Understanding the driving forces behind these interactions at the molecular level is essential.
• Graphene's unique properties make it an important model system for studying interfacial phenomena.

Purpose of the Study:

• To investigate the length-scale dependence of hydrophobic interactions between graphene sheets.
• To elucidate the roles of entropy and enthalpy in graphene association.
• To quantify the impact of water molecules on graphene interactions.

Main Methods:

• Molecular dynamics simulations were employed to model graphene sheets of varying sizes.
• Thermodynamic properties, including enthalpy and entropy, were analyzed.
• The potential of mean force was calculated to understand interaction potentials.

Main Results:

• Hydrophobic interaction driving force is length-scale dependent, even without dewetting.
• Small hydrophobes associate entropically, while large graphene sheets associate enthalpically.
• Water-induced stabilization and hydrogen bonding changes were quantified with increasing graphene surface area.

Conclusions:

• The transition from entropic to enthalpic dominance occurs around 0.3-1.5 nm(2) of eliminated surface area.
• Thermodynamic properties and interaction potentials exhibit scaling behavior with surface area in the large-scale regime.
• Graphene association influences water hydrogen bond dynamics and rearrangement, with longer lifetimes around small solutes.