When Does the Switch from Hydrotropy to Micellar Behavior Occur?

Lower alkanoates, alkyl sulfates, and alkylbenzenesulfonates behave as hydrotropes, while those with longer alkyl chains are micellar. We address the question of how long should the alkyl chain be in order for alkylbenzenesulfonates to switch from hydrotropy to micellar behavior. While surface tension and solubilization properties show a transition into micellar-type behavior beyond pentylbenzenesulfonate, microenvironmental features do not show any clear break between hydrotropes and micelles. The answer to the question thus seems to depend on the method used to monitor the properties.