On the cononsolvency behaviour of hydrophobic clusters in water-methanol solutions.

Simple calculations, grounded on the geometric approach to hydrophobic interaction, confirm the occurrence of a minimum in the Gibbs free energy change associated with the formation of several hard sphere clusters in water-methanol solutions with a methanol molar fraction of around 0.3, at room temperature and atmospheric pressure. This finding is in line with the computer simulation results of Mochizuki and Koga [Phys. Chem. Chem. Phys., 2016, 18, 16188]. However, it is underscored that these results cannot be the basis for a rationalization of the cononsolvency phenomenon of the polymers in water-methanol solutions. In fact, there is no Gibbs free energy minimum for the processes more closely resembling polymer collapse, i.e., those involving solely a change in the spatial organization of the same number of hard spheres.