Synthesis and characterization of swollen elastomer colloids

Swellable particles have a growing number of application as pigments, coatings and encapsulation agents. The swelling of a series of functionalized acrylic particles has been studied by a combination of Quasi-Elastic Light Scattering (QELS) and Scanning Electron Microscopy (SEM) techniques. The particles were prepared by the emulsion polymerization of buthyl acrylate (BuA), methyl methacrylate (MMA), and different percentages of acrylic acid (AA). All the reactions were carried out at a pH lower than 4 in order to ensure a whole incorporation of the functionalizing agent (AA). The obtained particles were submitted to an alkali treatment with three different swelling agents (NaOH, KOH and NH₄OH). SEM images revealed in all the cases an irregular increment of the particle diameter and a loss of the particle monodispersity, because of the expansion produced by the diffusion of the alkali into the particles. The micrographs also showed the formation of particles agglomerates, which constitutes evidence of a lower latex stability.