Generality of hydrophobic phenomena for aqueous solutions of amphiphiles

With the temperature and composition dependence of the isobaric heat capacity as our experimental probe, previously reported anomalous behaviors for tert-butanol and 2-butoxyethanol in water are shown to belong to a general scheme for aqueous solutions of amphiphiles. As opposed to a pretransitional scenario, our results point towards aggregation of the hydrophobic moieties of solute molecules as the origin of the phenomenology. The locus in the mole fraction-temperature plane that maps anomalies for 1-pentylamine solutions extends to quite small concentrations and 330 K, thereby raising questions on the roles of hydration and aggregation in phenomena involving so-called 'molecular hydrophobic interfaces'. (C) 2015 Elsevier B.V. All rights reserved.