Core-shell clusters: A new class of colloids for dynamic and structural studies

For over 60 years, since their essentially accidental synthesis in the late 1940s, the utility of suspensions of monodisperse, spherical colloids has been widely demonstrated throughout industry and academia. Colloidal spheres are of particular interest to researchers conducting fundamental studies because they can be regarded as effective atoms, their dynamics occur on experimentally realizable time scales and they can be observed using simple optical techniques. While suspensions comprised of spheres have long been the colloidal system of choice, the experimental and technological limitations of the sphere has sparked interest in the development of colloids with more complex shapes.;The goal of this dissertation was to develop a new class of non-spherical colloidal particles ideal for use in direct observation studies of dense suspensions. Today, confocal microscopy allows the direct observation of the structure and dynamics of dense colloidal suspensions to be probed on the single particle level. However, the confocal microscope also places stringent requirements on the colloidal suspension. Colloidal particles must be labeled with a fluorescent dye and ideally index- and density-matched to the suspending medium. While a small number of colloidal systems with the requisite properties for confocal studies have been developed, they almost all consist of only simple spherical particles and have experimental limitations. Here I present the synthesis of two distinct classes of sterically stabilized PMMA particles, consisting of a fluorescently labeled core and a large non-fluorescent shell (core-shell), ideal for confocal microscopy. The first class represents an improvement on the preexisting systems. The second is a new class of particles that can be used to fabricate colloidal clusters.;I show that by applying a well-known emulsion drying process to suspensions of my core-shell particles I can generate a new class of non-spherical, fluorescently-labeled clusters. The cluster fabrication process yields a unique and consistent structure for each cluster containing n particles. In addition, I use confocal microscopy and readily available tracking algorithms to demonstrate the ability to locate and track the motion of individual particles within a cluster as a function of time.