Hydrotropes

The concepts hydrotrope and hydrotropy are reviewed with a strong focus on the literature from recent years. The action and physical-chemical behavior of hydrotropes are discussed in relation to co-solubilizers and surfactants. A definition of a hydrotrope is formulated, and it is demonstrated that the unique behavior of a hydrotrope, which distinguishes this class of substances from both co-solubilizers and regular surfactants, is that the aggregation is weak without a hydrophobic solute, but there is a pronounced aggregation in the presence of a hydrophobic solute. (C) 2016 Elsevier Ltd. All rights reserved.