Microencapsulation, controlled release surface

Microencapsulation techniques are now being actively developed along directions that will have an important impact on electrochemically based industries. Possibilities include the masking of particulate surfaces to prevent specific (and undesirable) reactions as well as the controlled release of electroactive components or inhibitors into the environment (24). The following examples illustrate these techniques. 

Figure 4. Microencapsulation technique for controlled release of pesticides from a polymeric surface...

One may list a large number of surface chemical phenomena that are crucial in the preparation of more complex systems such as multiple emulsions and microcapsules. In the first case, the formulation is a complex system of an emulsion in an emulsion , with the most common being a water-in-oil-in-water (W/O/W) multiple emulsion, which requires the preparation of a stable W/O emulsion that is further emulsified into an aqueous solution of another surfactant to produce the final system. Microencapsulation is a process whereby the active ingredient is surrounded by a polymer shell that allows the controlled and slow release of the active. The most common procedure for encapsulation is interfacial polymerization, whereby two monomers are allowed to react at the interface (by condensation) to produce the... 

Controlled drug release properties are achieved through the application of coating to the surface of the capsule. A surface coating is applied in a microencapsulation process that frequently uses a plasticized aciylic copolymer. The type and concentration of plasticizer determines the rate of drag release. Trietltyl citrate is a typical plasticizer used in such microencapsulation. 

Other kinds of microencapsulation also provide means for transporting and controlling the release of chemical species in a variety of applications, from pharmaceuticals to cosmetics to agrochemicals [142]. The microencapsulating surface, or barrier, can be ... 

---