Micelles from the ionic surfactants can be formed only above a certain temperature called as:  

CONCEPT:

Micelle Formation and Krafft Temperature

• Micelles are aggregates of surfactant molecules that form in a solution above a certain concentration and temperature.
• For ionic surfactants, micelle formation occurs only above a specific temperature called the Krafft temperature.
• The Krafft temperature is the temperature below which the surfactant molecules remain in crystalline form and do not form micelles, even if the concentration is above the critical micelle concentration (CMC).

EXPLANATION:

• Surfactants are amphiphilic molecules, meaning they have both hydrophobic and hydrophilic parts.
• At temperatures below the Krafft temperature:
  • The solubility of the surfactant is too low to allow micelle formation.
  • The surfactant remains in a solid crystalline state.
• At temperatures above the Krafft temperature:
  • The solubility increases, and micelle formation becomes possible when the surfactant concentration exceeds the CMC.
  • Micelles act as carriers for hydrophobic substances in aqueous solutions.
• The Krafft temperature is specific to the surfactant and its chemical structure.

Therefore, micelles from ionic surfactants can be formed only above a certain temperature called the Krafft temperature.