ASSEMBLY OF LATEX-PARTICLES BY USING EMULSION DROPLETS AS TEMPLATES .1. MICROSTRUCTURED HOLLOW SPHERES

We describe an emulsion-based technique that allows the assembly of co lloid particles into microstructured or multicomponent clusters (''sup raparticles''). The particles are gathered, assembled, and fixed toget her in the restricted, colloid-size 2D or 3D space provided by emulsio n droplets. The process is carried out by multiple modification of the colloid interactions within the particle/droplet system-''interaction -tailored colloid assembly''. In the first paper of the series we prov ide a general description of the method. Then we present the data on t he assembly of negatively charged (sulfate) or positively charged (ami dine) latexes into ordered hollow spherical supraparticles. The follow ing steps are included in the assembly schemes: (1) modification of la tex surface charge and properties, so the microspheres are able to ads orb on the droplet surfaces but without homocoagulation; (2) adsorptio n and structure formation around the emulsion drops (at this stage the interfacial mobility of the particles is of crucial importance); (3) sterical protection of the particle/droplet complexes against coagulat ion or flocculation; (4) ''binding'' of particles within the assembled microspheres by strong coagulant; (5) extraction of the supraparticle s by dissolving the carrier droplets in the surrounding environment. T o characterize the electrostatic interactions throughout the assembly stages, we used electrophoretic mobility measurements. The electrophor etic data are in good qualitative agreement with the interaction-tailo red assembly scheme. Clues on the other interactions involved are prov ided by altering the assembly process and using different modifying ag ents.