Od. Velev et al., ASSEMBLY OF LATEX-PARTICLES BY USING EMULSION DROPLETS AS TEMPLATES .1. MICROSTRUCTURED HOLLOW SPHERES, Langmuir, 12(10), 1996, pp. 2374-2384
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.