  The lifetime of a hydrogen bond between water and dimethyl sulfoxide (DMSO)
is found to be considerably longer than that between two water molecules in the
neat water. This is counter-intuitive because the charge on the oxygen in DMSO
is considerably less than that in water. Additionally, the strength of the
water-dimethyl sulfoxide (w-D) hydrogen bond is found to be strongly
composition dependent; the lifetime of the hydrogen bond is ten times larger at
30% over that at very low concentration. Using computer simulations, we perform
microscopic structural and dynamic analysis to find that these anomalies arise
at least partly from an action-at-a-distance effect where the attraction
between the hydrophobic methyl groups results in self-aggregation of DMSO
molecules that cages both rotational and linear motions of molecules involved.
This is reflected in the observed strong correlation of the lifetime with the
local coordination number of the associated methyl groups. The elongated w-D
h-bond lifetime causes a slowdown of collective dynamics and affects the
lifetime of the w-w h-bond. This nonlinear feedback mechanism explains the
strong composition dependence of viscosity and anticipated to play a dominant
role in many self-assemblies. Furthermore, the w-D hydrogen bond breaking
mechanism changes from low to high DMSO concentration, a phenomenon not
anticipated a priori. We introduce a new order parameter-based free energy
surface of the bond breaking pathway. A two-dimensional transition state rate
theory (TSRT) calculation is performed for the lifetime of the w-D h-bond that
is found to be semi-quantitatively accurate
