Preparation of microspheres and microcapsules by interfacial polycondensation techniques.

A methodological review of the production of microspheres/microcapsules by interfacial polycondensation is presented and the mechanisms of particle and capsule formation are discussed. Procedures for interfacial polycondensation employed for the preparation of microspheres/microcapsules involve the polycondensation of two complementary monomers in a two phase suspension system. Each of the two complementary monomers resides largely in one of the two immiscible phases in the suspension system. The resulting polycondensate, which is formed at or on one side of the interface, may, or may not, be soluble in the droplet phase. If the polymer is soluble in the droplets, particulate microspheres or monolithic microcapsules are formed, i.e. particle forming interfacial polycondensation. If the polymer is insoluble in the droplets, it forms a membrane around them, and the droplets are thus individually encapsulated by the polymer. This leads to the formation of capsular microspheres or reservoir microcapsules, and hence capsule forming interfacial polycondensation. A major example of particle forming interfacial polycondensation is that of phosgene with bisphenol A recently developed for the production of polycarbonate resins in particle form. Capsule forming interfacial polycondensation is widely used to prepare polyamide (nylon) microcapsules containing proteins, pharmaceuticals, etc.