Influence of Polymers on Colloidal Stability

Polymers are often applied to promote either stabilization or aggregation. Examples of polymer-induced aggregation are found in water purification, clarification of wine and fruit juices, and in papermaking. Stabilization of colloidal particles by polymers is applied in foodstuffs, paints, and dyes, in the dispersion of particles on magnetic tapes and photographic paper, as well as in many cosmetic and medical salves and lotions. A rather recent development is the use of polymers to reduce or prevent the deposition of protein molecules and biological cells on surfaces in order to avoid biofouling and, hence, improve the biocompatibility of these surfaces. 

Because of the complex influence of polymers on colloidal stability, we will treat this subject on a qualitative or, at best, semiquantitative level. 

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Initial experiments with polymers between the mica sheets were complicated by surface diffusion and exchange or fractionation of the polymers. With the use of more monodisperse polymers, the technique is now demonstrating good qualitative agreement with theory, and is being used to confirm predictions of the influence of polymers on colloid stability. 

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