Steric Stabilization

Steric stabilization by polymers adsorbed on inorganic particle surfaces is gaining more and more attention in both industry and academia because it plays an important role in stabilizing colloidal dispersions. In this review, basic concepts and some related topics about steric stabilization are introduced. In addition the application of steric stabilization in dispersing ceramic particles in non-aqueous media is summarized. It is found that functional groups, such as carboxyl, hydroxyl, amine, and ester groups in the molecular polymer structure generally play an important role in steric stabilization. Polymers containing carboxyl groups turn out to be the most effective steric stabilizers because carboxyl groups are supposed to interact strongly with basic sites, often present on the particle surface. On the other hand, the long chain hydrocarbons in the molecular structures extend from the surface into nonaqueous solvent and act as good moieties in nonaqueous media. The longer the hydrocarbon chains, the better the stabilization effect. It is also shown in the literature that copolymers are usually more effective in steric stabilization than homopolymers because copolymers consist of more than one type of repeated unit. One type of repeated unit can act as anchor; the other type can act in the moieties extending into a nonaqueous solution. Steric stabilization in the modified emulsion precipitation method to prepare ceramic nanoparticles is discussed at the end of this review. Poly(octadecyl methacrylate) (PODMA) is used as the steric stabilizer in that method. It is suggested that the ceramic nanoparticles are stabilized by a bilayer of polymer (PODMA) and surfactant (DiDAB). The exact stabilization mechanism still needs further study.