Controlled Flats on Spherical Polymer Colloids

Abstract

Colloidal particles with heterogeneous surfaces offer rich possibilities for controlled self-assembly. We have developed a method for preparing micrometer-sized polystyrene spheres with circular flat spots of controlled radius and location. The flats are created by settling the particles onto a flat glass substrate and then raising the temperature above the glass-transition temperature of the polymer for a controlled time (t). The polymer particle spreads on the glass such that the radius of the flat grows with time. We present a scaling theory for the hydrodynamics of the flattening process, finding that the radius of the flat grows as t(1/3). The model is in good agreement with our experimental observations of the flat radius versus spreading time as well as with previous studies in the literature for sintering polymer spheres.

Facile Fabrication of Anisotropic Colloidal Particles with Controlled Shapes and Shape Dependence of Their Elastic Properties

“…With a specific exposure time when the solvent vapor reached the saturated pressure, there was enough solvent vapor interacting with the polymer particles. The solvent molecules added free volume to the polymer chains, increasing the polymer segmental mobility and thus causing a depression in the glass transition temperature of the chains . When the glass transition temperature of the chains was decreased to the ambient temperature, the polymer chains went from the glassy state to rubbery state, where the movements of polymer chain segments were greatly intensified and the elasticity of the polymer chains was increased.…”

Formation of Carbonized Polystyrene Sphere/hemisphere Shell Arrays by Ion Beam Irradiation and Subsequent Annealing or Chloroform Treatment

“…Only a coalescence phenomenon of neighboring PS microspheres occurred when the irradiated fluence reached 7 × 10 16 ions/cm 2 . According to the existing studies about various methods for sintering colloidal particles 19 26 27 28 , the coalescence or neck formation results from the reduction of surface free energy under high temperatures. Therefore, we chose this irradiated fluence (7 × 10 16 ions/cm 2 ) in subsequent experiments and attempted to change the energy to investigate the influence of ion-irradiated energy on the morphology of PS spheres.…”

Detection of 4′,6-diamidino-2-phenylindole within silver-doped silica sol- and aerogels using surface-enhanced Raman spectroscopy

“…Substitution of the chloride for a carbonate or methylcarbonate may be occurring during supercritical drying. In addition amidines are known to hydrolyze upon heating in aqueous solution to initially form amides and then carboxylic acids [38,39]. The peak could also be due to the reaction of DAPI to form the carboxylic acid salt during the supercritical drying process.…”