Relationship between solubility and micellization of surfactants: The temperature range of micellization

Many technical terms relating the solubility of surfactants with their aggregation as micelles are reviewed in order to derive a consistent concept of this relation, and the reason why the micelle temperature range (MTR) can clarify the relation between solubility and micellization of surfactants better than the Krafft point is given. It is also made clear that the temperature range for the MTR is based on the concentration range of cmc, which in turn results from the polydispersity of micelles. From the concept of MTR, there exist in principle two ways to decrease the MTR: one is to increase monomeric solubility of surfactants while leaving cmc unchanged and the other is to decrease cmc values of surfactants while leaving monomeric solubility unchanged. These are examined by the Gibbs’ phase rule for surfactant solutions and by using many experimental results.