Rheological studies on sterically stabilized dispersions of uniform colloidal spheres: I. Sample Preparation

Abstract

A series of model colloidal dispersions was prepared in which uniform poly(methylmethacrylate) spheres of four different particle sizes were dispersed in heptane and in three different silicone oils. Polymerization was carried out in hexane, using as stabilizers well-characterized tri-block copolymers in which the end blocks were poly(dimethylsiloxane) and the central block was polystyrene. The dispersions were cleaned by successive centrifugations and decantations before redispersal in the silicone oils. Particle sizes were measured by both electron microscopy and photon correlation spectroscopy. Thickness of the adsorbed layer was determined from both intrinsic viscometry and as the difference between the hydrodynamic radius from photon correlation spectroscopy and the particle radius from electron microscopy.