Cosurfaktant

Cosurfaktant, or cosurfactant, is a substance used in combination with a surfactant to enhance the formation and stabilization of emulsions and microemulsions. Cosurfactants are typically smaller, more hydrophilic molecules that partition at the oil–water interface and modify the interfacial film. They reduce interfacial tension further and increase the fluidity of the interfacial layer, enabling easier disruption and reformation of droplets and often broadening the two-phase region in phase diagrams.

Common cosurfactants include short-chain alcohols (for example ethanol, propanol), glycols (propylene glycol, glycerol), and certain low-molecular-weight solvents. They are widely used in pharmaceutical and cosmetic formulations to help prepare stable microemulsions for solubilizing poorly soluble actives, and to tune rheology and permeation properties. In food and other applications, they can assist emulsification processes, though use is governed by safety and regulatory considerations.

Safety and regulatory considerations: cosurfactants can cause irritation or toxicity if used inappropriately; their selection depends on the target system, desired phase behavior, and regulatory constraints. They are typically used at lower concentrations than primary surfactants and may be removed or remain in the final product depending on the formulation.

In summary, cosurfactants are auxiliary agents that work with surfactants to improve emulsification efficiency, stability, and formulation performance in a range of industries.