Hydrophobicity and thermodynamic response for aqueous solutions of amphiphiles

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• 作者：Katerina Zemá ; nková ; ^a ; Jacobo Troncoso^a ; Claudio A. Cerdeiriñ ; a^a ; ^{calvarez@uvigo.es" class="auth_mail" title="E-mail the corresponding author} ; Luis Romaní ; ^a ; Mikhail A. Anisimov^b ; ^c
• 关键词：Water and aqueous solutions ; Hydrophobicity ; Amphiphiles ; Heat capacity ; Structural phenomena
• 刊名：Chemical Physics
• 出版年：2016
• 出版时间：15 June 2016
• 年：2016
• 卷：472
• 期：Complete
• 页码：36-43
• 全文大小：1777 K

文摘

The anomalous behavior of aqueous solutions of amphiphiles in the water-rich region is analyzed via a phenomenological approach that utilizes the isobaric heat capacity C_p$C_p$ as an experimental probe. We report extensive data for solutions of 14 amphiphiles as a function of temperature at atmospheric pressure. Beyond that, C_p$C_p$ data but also isobaric thermal expansivities and isothermal compressibilities for three solutions of tert  -butanol as a function of both temperature and pressure are presented. Results rule out the possibility that the observed phenomenology is associated with the anomalous thermodynamics of pure water. Indeed, our C_p$C_p$ data, quantitatively consistent with recent spectroscopic analyses, suggest that water-mediated interactions between the nonpolar parts of amphiphiles are at the origin of anomalies, with the effects of such “hydrophobic aggregation” being observed at mole fractions as small as 0.01. Physicochemical details like the size, the electronic charge distribution and the geometry of amphiphile molecules as well as third-order derivatives of the Gibbs energy and the associated Koga lines support the above claims while they further contribute to characterizing the role of hydrophobicity in these phenomena. Progress with a view to gain a deeper, more concrete understanding remains.