Non-ideality of amphiphilic binary mixtures

If the nature of the moleeules constituting the binary mixture is not too different from each other, such as a mixture of methane and ethane, then the mixture behaves ideally and follows Raoult s law. According to Raoult s law, a property of a mixture is given by the addition of weighted contributions [1] 

In general, however, this simple Raoult s law is found to be inadequate for many practical applications. Interestingly, the most notable deviation is provided by those binary solutions that we discuss in the current chapter, that is, where the solute is amphiphilic in nature These deviations reveal information about the intermolecular interactions and also the molecular arrangement in these mixtures. The deviations can be of various kinds, positive, negative and complex, showing both a maximum and a minimum. 

In aqueous DMSO solution, there surprisingly exist two ranges of compositions where the concentration dependence of many properties exhibits non-monotonic changes in their behavior. One of this occurs in the -35 0% DMSO concentration (mole percentage) range and the other takes place at a lower DMSO eoneentration range, 10-15%. 

The anomalies near the high concentration range have been investigated by extensive computer simulation studies to understand the moleeular origin of the anomalies observed in the thermodynamic, dielectric, and dynamic properties in the said concentration range [3,4]. For example, both the shear viseosity and the thermal conductivity of the mixture have been analyzed and eompared with available experimental data under ambient conditions. The enhaneement of shear viseosity at mole fraction = 0.65 (xdmso 0.35) has been quantitatively reprodueed in simulations [5]. 

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