title: Micro-heterogeneity versus clustering in binary mixtures of ethanol with water or alkanes.
abstract: Ethanol is a hydrogen bonding liquid. When mixed in small concentrations with water or alkanes, it forms aggregate structures reminiscent of, respectively, the direct and inverse micellar aggregates found in emulsions, albeit at much smaller sizes. At higher concentrations, micro-heterogeneous mixing with segregated domains is found. We examine how different statistical methods, namely correlation function analysis, structure factor analysis and cluster distribution analysis, can describe efficiently these morphological changes in these mixtures. In particular, we explain how the neat alcohol pre-peak of the structure factor evolves into the domain pre-peak under mixing conditions, and how this evolution differs whether the co-solvent is water or alkane. This study clearly establishes the heuristic superiority of the correlation function/structure factor analysis to study the micro-heterogeneity, since cluster distribution analysis is insensitive to domain segregation. Correlation functions detect the domains, with a clear structure factor pre-peak signature, while the cluster techniques detect the cluster hierarchy within domains. The main conclusion is that, in micro-segregated mixtures, the domain structure is a more fundamental statistical entity than the underlying cluster structures. These findings could help better understand comparatively the radiation scattering experiments, which are sensitive to domains, versus the spectroscopy-NMR experiments, which are sensitive to clusters.
authors.affiliation: Laboratoire de Physique Théorique de la Matière Condensée (UMR CNRS 7600), Université Pierre et Marie Curie, 4 Place Jussieu, Paris cedex 05, F75252, France. aup@lptmc.jussieu.fr and Department of Physics, Faculty of Sciences, University of Split, Ruđera Boškovića 37, Split, 21000, Croatia.
authors.forename: Martina
authors.initials: M
authors.lastname: Požar
authors.affiliation: Department of Physics, Faculty of Sciences, University of Split, Ruđera Boškovića 37, Split, 21000, Croatia.
authors.forename: Bernarda
authors.initials: B
authors.lastname: Lovrinčević
authors.affiliation: Department of Physics, Faculty of Sciences, University of Split, Ruđera Boškovića 37, Split, 21000, Croatia.
authors.forename: Larisa
authors.initials: L
authors.lastname: Zoranić
authors.affiliation: Department of Physics, Faculty of Sciences, University of Split, Ruđera Boškovića 37, Split, 21000, Croatia.
authors.forename: Tomislav
authors.initials: T
authors.lastname: Primorać
authors.affiliation: Department of Physics, Faculty of Sciences, University of Split, Ruđera Boškovića 37, Split, 21000, Croatia.
authors.forename: Franjo
authors.initials: F
authors.lastname: Sokolić
authors.affiliation: Laboratoire de Physique Théorique de la Matière Condensée (UMR CNRS 7600), Université Pierre et Marie Curie, 4 Place Jussieu, Paris cedex 05, F75252, France. aup@lptmc.jussieu.fr.
authors.forename: Aurélien
authors.initials: A
authors.lastname: Perera