Self assembly of anisotropic colloidal particles

Article · February 2012with3 Reads


    Colloidal particles have been successfully used as ''model atoms'', as
    their behavior can be more directly studied than that of atoms or
    molecules by direct imaging in a confocal microscope. Most studies have
    focussed on spherical particles with isotropic interactions. However, a
    range of interesting materials such as many supramolecular polymers or
    biopolymers exhibit highly directional interactions. To capture their
    behavior in colloidal model systems, particles with anisotropic
    interactions are clearly required. Here we use a colloidal system of
    nonspherical colloids, where highly directional interactions can be
    induced via depletion. By biaxially stretching spherical PMMA particles
    we create oblate spheroidal particles. We induce attractive interactions
    between these particles by adding a non-adsorbing polymer to the
    background liquid. The resulting depletion interaction is stronger along
    the minor axis of the oblate spheroids. We study the phase behavior of
    these materials as a function of the ellipsoid aspect ratio, the
    strength of the depletion interactions, and the particle concentration.
    The resulting morphologies are qualitatively different from those
    observed with spherical particles. This can be exploited for creating
    new materials with tailored structures.