Revealing microheterogeneities and second order phase transitions in aqueous mixtures of 1-propoxypropan-2-ol at 298 K.

Second order phase transitions corresponding to discontinuities in the plots of Kirkwood-Buff integrals as a function of composition were observed in aqueous mixtures of the amphiphilic molecule, 1-propoxypropan-2-ol, revealing the formation of hydrophobic aggregates and generating microheterogeneities over a limited range of compositions. Electrospray mass spectra, surface tension measurements and solvatochromic parameters confirmed the onsets of different aggregation patterns over the entire composition range, and allowed us to scrutinize the prevailing types of aggregate species. This is seemingly the first time that such discontinuities are clearly assumed as second order phase transitions in a system macroscopically homogeneous and corroborated by other independent tools.