Preparation and characterization of poly(methyl methacrylate) beads

For fluid-dynamic experiments involving concentrated suspensions and complex geometries, particles which are neutrally buoyant and which have the same refractive index as both the suspending fluid and the bounding container are needed. Poly(methyl methacrylate) (PMMA) particles can meet these requirements simultaneously. Therefore monodisperse beads with the refractive index and density of pure PMMA were needed. For comparison with particle migration theory, it is also important that bead size and sphericity be accurately controlled. In our fluid mechanics experiments, 500-μm diameter was required, a size where suspension polymerization is suitable. This article describes the controlled formation of PMMA beads in substantial quantities with desired size and a narrow particle size distribution. Reaction scale-up using a 2-L Buchi reactor allowed batch yields of 200 g of PMMA beads with desired shape and size. However, microcavities reduced bead density and optical clarity. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008