Hysteresis of conductivity in a micellar surfactant solution near the Krafft point

The specific conductivity of aqueous cetyltrimethylammonium bromide solutions has been investigated below and above the critical micelle concentration, in order to elucidate slow structural changes. Around the Krafft temperature (approximate to 25 degrees C) the monomer solubility reaches the critical micelle concentration, and a significant increase in charge transport is recorded. When a temperature decreases, the micellar surfactant solution passes through the Krafft temperature, and a hysteresis phenomenon is observed with the appearance of crystals in a solution. We have scrutinized the conditions leading to this hysteresis and quantified some of the relevant parameters. We also outline a simple procedure that allows the "erasure" of such structural memory effects, which are potentially detrimental to the formation of adsorbed self-assembled monolayers from solution.