Transport properties of dimethyl sulfoxide aqueous solutions

The nonideal behavior of the transport properties of water-dimethyl sulfoxide (DMSO) mixtures has been studied through equilibrium and nonequilibrium molecular dynamic simulations. The shear viscosity and thermal conductivity of the mixture has been analyzed and compared with available experimental data at ambient conditions. The enhancement of shear viscosity at molar fractions x(W)=0.65 of water has been quantitatively reproduced in our simulations. In agreement with this fact, we have found an increase in the rigidity of the system reflected by an increase in the decay time of the survival probability of the H bonds. In addition, we compute the tetrahedral order parameter of water molecules in the solution at different molar fractions. This parameter indicates a reduction in the local tetrahedral order of water when the solute concentration is increased, followed by a clear minimum at the equimolar concentration near the locus of the maximum density of the mixture, probably due to the formation of water-DMSO complexes. We have obtained the thermal conductivity of the mixture for the first time. This property also presents a peculiar minimum at x(W)=0.4, precisely in the region of the minimum of the order parameter. However, no experimental confirmation of our results is available. (C) 2003 American Institute of Physics.