Hydrogen Bond Dynamics Near A Micellar Surface: Origin of the Universal Slow Relaxation at Complex Aqueous Interfaces

TL;DR

This study uses molecular dynamics simulations to reveal that hydrogen bonds at micellar surfaces have significantly longer lifetimes than those among water molecules, explaining the universal slow relaxation observed at complex aqueous interfaces.

Contribution

It demonstrates that hydrogen bonds between water and polar head groups at micellar surfaces are notably longer-lived, providing insight into slow relaxation phenomena at hydrophilic interfaces.

Findings

Hydrogen bonds between water and PHG are longer-lived than water-water bonds.

Water molecules can stay bound to micellar surfaces for over 100 ps.

Activation energy for water detachment is approximately 3.5 kcal/mol.

Abstract

The dynamics of hydrogen bonds among water molecules themselves and with the polar head groups (PHG) at a micellar surface have been investigated by long molecular dynamics simulations. The lifetime of the hydrogen bond between a PHG and a water molecule is found to be much longer than that between any two water molecules, and is likely to be a general feature of hydrophilic surfaces of organized assemblies. Analyses of individual water trajectories suggest that water molecules can remain bound to the micellar surface for more than a hundred picosecond. The activation energy for such a transition from the bound to a free state for the water molecules is estimated to be about 3.5kcal/mole.