Study of the anomalous particles formed during the surfactant‐free emulsion polymerization of styrene

Abstract

Abstract The presence of anomalous regions within polystyrene latex particles prepared in the absence of added emulsifier has been investigated. It appears that they arise through loss of monomer from particles consisting of a discrete monomer‐rich region surrounded by a polymer shell. It is likely that in most cases, monomer is lost from the region on evacuation prior to electron microscope examination, although there is some evidence from γ‐irradiated samples (prior to electron microscopy) that loss of monomer can also occur during storage and/or dilution of the sample. Scanning electron microscopy and carbon replication techniques have been used to determine the shapes of the voids. Gas adsorption studies and carbon replication have also served to illustrate that the presence of the regions was not due to electron‐beam damage. The presence of extrusions on some samples has been attributed to incomplete loss of monomer on evacuation due to the thickness of the surrounding polymer shell.