Imaging homogeneous and composite latex particles with an atomic force microscope

To investigate the morphology of individual latex particles with the atomic force microscope, the particles were adsorbed onto mica and then dried. Homogeneous and composite latex particles were studied. The particles were made of different amounts of poly(butyl acrylate) and poly(methyl methacrylate) yielding different viscoelastic properties and different morphologies. During adsorption and subsequent drying, the packing of the particles is probably mainly determined by capillary forces; their deformation is caused by interfacial forces. The shape of the particles on the mica surface depends on their original morphology and their viscoelastic properties. In addition, films formed with the latex particles were imaged to correlate the structure of individual particles with that of the film surface. In two layers we observed significant deformation of the latex particles although the layer was formed far below the minimum film formation temperature. Vice versa, in one film formed above the minimum him formation temperature no deformation-induced reduction of the nearest neighbor distance was observed.