Koazervierung

Koazervierung, anglicized as coacervation, is a phase separation phenomenon in colloid and polymer science. In coacervation, a homogeneous polymer solution separates into two liquid phases: a polymer-rich coacervate phase and a polymer-lean equilibrium phase. The coacervate is typically immiscible with the surrounding medium, enabling capture of dispersed core material.

There are two main forms of koazervierung. Simple coacervation occurs when changes in solvent quality, temperature, or ionic strength reduce polymer solubility, causing the formation of coacervate droplets. Complex coacervation arises from electrostatic attraction between two oppositely charged polyelectrolytes, such as gelatin and gum Arabic, forming a coacervate phase that can entrap solid or liquid cores.

Process overview typically involves several steps. First, an aqueous solution of the polymer(s) is prepared and the core material is dispersed if encapsulating a substance. Then coacervation is induced by adjusting conditions, leading to the condensation of polymer droplets around the core material. Finally, the droplets are stabilized and hardened by cross-linking, drying, or solvent removal to yield microcapsules.

Applications of koazervierung include microencapsulation for controlled release of flavors, fragrances, essential oils, pharmaceuticals, and agricultural chemicals. The technique is also used for protecting sensitive active ingredients and for encapsulation in cosmetics and food products.

Advantages and limitations include the ability to operate under mild conditions and achieve high encapsulation efficiency for delicate actives, while being sensitive to temperature, pH, and ionic strength. Controlling particle size distribution and achieving stable long-term formulations can present challenges, sometimes necessitating stabilizers or precise process control.

Historically, koazervierung emerged from early 20th-century colloid science research into encapsulation using natural polymers and has since become a common method in materials science and pharmaceutical technology.