This review is devoted to the phenomenon of mesoscale solubility, meaning that chemical compounds can solubilize (fill homogeneously the whole volume of the system) not only via molecular solvation based on the principle “like likes like”, but also via mesoscale solubilization of dislike solvophobic compounds. This type of solubilization proceeds via formation of mesoscale structures with dimensions between molecular and macro scale, respectively. They have variable temporal stability up to complete long-term stability, comparable to the molecular solvation concept. Once the solute is sufficiently solvophobic to generate mesoscale structures, it is at the same time capable to yield sufficient surface zeta potentials needed for their stabilization. This generation and stability is given solely by solvophobicity, hence we refer to these structures as solvophobicity-driven mesoscale structures (SDMSs). Nothing else than solvophobicity is needed. Two historical routes to the study of this phenomenon are described. One originated from an effort to understand a surprising spontaneous existence of structures of unknown origin in binary systems and the second one originated from the study of the ouzo effect (mixing ouzo beverage with water). The physical background of SDMSs is discussed with focus on various ways of SDMS formation, phase diagrams including nonaqueous mixtures, ouzo-derived particles specifics, the role of hydrotropes, advanced characterization of SDMS size distributions and shape, droplets vs. solid particles, basic parameters influencing SDMS, surface zeta potential as a basis of SDMS stability, relation to surfactant-free microemulsions, and remarks concerning methodological issues and bottlenecks of the research in this field. • Solvophobic compounds can solubilize mesoscopically • Concentrations reached are orders of magnitude higher than those reached molecularly • This is done spontaneously without surfactants or other stabilizers • The key stabilizing factor is spontaneous surface charging of particles • Resulting nano- or submicron-sized particles and droplets have interesting properties
Marián Sedlák (Sun,) studied this question.