Preparation of nano- and microspheres by polycondensation techniques

Particle-forming polycondensation techniques can be divided into two main categories, namely normal polycondensation and interfacial polycondensation. Various normal polycondensation procedures employed for the preparation of nano- and microspheres are covered by this review, and are described under suspension polycondensation, dispersion polycondensation and precipitation polycondensation. Among these, suspension polycondensation procedures are generally applicable for the preparation of both nano- and microspheres. They are employed for the production of industrially important polycondensates such as phenolics, polyesters and polyurethanes, as well as for novel polymeric materials such as polycyclodextrins, mercury-binding polymercaptals, and polyurea microcapsules. Dispersion polycondensation leads to the formation of monodisperse nanoparticles, but it is not widely employed. Precipitation polycondensation produces non-spherical and polydisperse particles, and it is useful only if low molecular weights of the polymer and polydispersity of the particles do not adversely affect the intended application of the product.