Applications of environmental scanning electron microscopy to colloidal aggregation and film formation

Environmental scanning electron microscopy (ESEM) is a rather new form of electron microscopy, which permits the observation of hydrated samples in their native state, and also does not require that insulators are coated with a conducting layer. These two factors make it ideal for studying colloidal dispersions as they aggregate and/or film form. This paper describes the application of ESEM to three situations involving aggregating latices. Firstly the nature of fractal structures grown from aggregating acrylic latices is discussed, with a comparison given of the behaviour with and without added salt as the screening between particles is altered. Secondly the behaviour of vinyl latices is considered. The impact of the addition of starch, both modified and unmodified, upon the particle size distribution and ability to film form is examined. Finally, the structures which form when the hard inorganic component silica is added to acrylic latices are explored. Together these three examples illustrate some of the many strengths of the ESEM in the field of colloidal dispersions and aggregates.