Krafft temperature
Encyclopedia
The Krafft temperature is the minimum temperature
at which surfactant
s form micelle
s. Below the Krafft temperature, there is no value for the critical micelle concentration
(CMC), i.e., micelles cannot form. The Krafft temperature is a point of phase change below which the surfactant remains in crystalline form, even in aqueous solution.
Surfactants in such a crystalline state will only solubilize and form micelles if another surfactant assists it in overcoming the forces that keep it crystallized, or if the temperature increases, thus causing entropy to have a stronger force and encouraging the crystalline structure to break apart.
The Krafft point is named after German chemist Friedrich Krafft
.
Increasing the length of the hydrocarbon chain increases the Krafft temperature because it improves Van der Waals
forces.
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
at which surfactant
Surfactant
Surfactants are compounds that lower the surface tension of a liquid, the interfacial tension between two liquids, or that between a liquid and a solid...
s form micelle
Micelle
A micelle is an aggregate of surfactant molecules dispersed in a liquid colloid. A typical micelle in aqueous solution forms an aggregate with the hydrophilic "head" regions in contact with surrounding solvent, sequestering the hydrophobic single tail regions in the micelle centre. This phase is...
s. Below the Krafft temperature, there is no value for the critical micelle concentration
Critical micelle concentration
In colloidal and surface chemistry, the critical micelle concentration is defined as the concentration of surfactants above which micelles form and almost all additional surfactants added to the system go to micelles....
(CMC), i.e., micelles cannot form. The Krafft temperature is a point of phase change below which the surfactant remains in crystalline form, even in aqueous solution.
Surfactants in such a crystalline state will only solubilize and form micelles if another surfactant assists it in overcoming the forces that keep it crystallized, or if the temperature increases, thus causing entropy to have a stronger force and encouraging the crystalline structure to break apart.
The Krafft point is named after German chemist Friedrich Krafft
Friedrich Krafft
Friedrich Krafft was a German chemist. He studied with Friedrich August Kekulé von Stradonitz, Rudolf Clausius and Gerhard vom Rath....
.
Structural Effects
Surfactants are usually composed of a hydrocarbon chain and a polar head group.Increasing the length of the hydrocarbon chain increases the Krafft temperature because it improves Van der Waals
Van der Waals force
In physical chemistry, the van der Waals force , named after Dutch scientist Johannes Diderik van der Waals, is the sum of the attractive or repulsive forces between molecules other than those due to covalent bonds or to the electrostatic interaction of ions with one another or with neutral...
forces.