Cosurfaktanter

Cosurfaktanter, or cosurfactants in English, are additives used together with primary surfactants to improve emulsions, foams, and microemulsions by further reducing interfacial tension and modifying the interfacial film and curvature. They help increase the stability of dispersed systems and broaden the range of compositions over which stable phases form.

Mechanism: Cosurfaktants partition to the oil–water interface, where their small size and polarity reduce interfacial tension to very low levels and increase interfacial fluidity. This aids in achieving favorable interfacial curvature and enables the formation of bicontinuous or nanoemulsion structures, facilitating emulsification and self-assembly.

Common cosurfactants: Typical cosurfactants include short-chain alcohols such as ethanol and propanol; glycols such as propylene glycol and glycerin; and other small polar molecules that readily partition at interfaces. Some non-ionic ethoxylated compounds can also act as cosurfactants in specific systems.

Applications: Cosurfaktanter are widely used in cosmetic and pharmaceutical formulations to improve the stability and drug delivery of microemulsions and topical products. They are also employed in detergents, cleaners, and some food-grade emulsions where regulatory acceptance allows their use, contributing to improved emulsification and foaming performance.

Considerations: The choice of cosurfactant depends on compatibility with the primary surfactant, the desired interfacial properties, and regulatory and safety constraints. Other considerations include potential effects on rheology, color, odor, toxicity, and long-term storage stability, as well as cost and supply.