Calorimetric Evidence about the Application of the Concept of CMC to Asphaltene Self‐Association

For many years, the concept of critical micellar concentration (CMC) has been projected from surfactant science into asphaltene science. There are several similarities between these two species, such as the stabilization of water‐in‐oil emulsions and surface activity, which suggested that asphaltenes may also have a concentration at which self‐association occurs (CMC). This article presents evidence found by calorimetry and spectroscopic techniques, that suggest that this concept may not be adequate for asphaltene self‐association in toluene solutions. Isothermal titration calorimetry has been widely used in surfactant science to determine both the CMC and the enthalpy of micellation of many surfactants. The concentration interval could be divided into three regions: monomer region, micellation region, and micelle region. The absence of the first region (monomer) in the concentration range usually found in the literature as the CMC region of asphaltenes indicates that this concept is not appropriate for a...