Polystyrene grafted silica dispersions

Figure 4.23 TEM images of polystyrene-coated MPS-grafted silica beads obtained through dispersion polymerization using...

Steric stabilization is another well-established method of stabilizing colloidal suspensions of submicron to micron size [23]. The particles are coated with a layer of adsorbed or grafted polymer chains that provides a steric repulsion of entropie origin and helps disperse the particles by counterbalancing van der Waals attraction (Fig. la). The polymeric nature of the adsorbed or grafted layer softens the interparticle interactions and makes the particles intrinsically deformable. Many polymer chain/particle combinations have been synthesized and studied, and are described in the literature. Several popular colloidal systems consist of silica particles covered with various polymers such as polydimethylsiloxane [24], stearyl alcohol [25], alkyl chains [26], and polyethylene oxide [27]. Polymethylmethacrylate and polystyrene particles grafted with polymer chains have also been used extensively. For a review on the impressive literature on the subject we refer the interested reader to Vlassopoulos and Fytas [2]. 

The systems studied by Clarke and Vincent (1981a) were closely analogous to those of de Hek and Vrij mentioned previously. Polystyrene was grafted on to silica particles by an anionic polymerization technique. Its molecular weight lay in the range S 000 to 24 000. The diameter of the monodisperse silica particles was varied from ca 100 to 300 nm. Ethyl benzene was chosen as the dispersion medium. 

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