Multihollow micron-sized latex particles from self-emulsifying polymer blends

This paper describes a new process for the preparation of micron-sized latex particles with multihollow structures. It is based on blends of solution polymers, which are self-emulsifying in water and form secondary dispersions. Their chemical composition leads to the formation of a multiple W/O/W-emulsion when the highly viscous polymer solution is emulsified in water. The particle size of the multiple emulsion droplets is in the micron range. The mechanism for the formation of the structures as described above was proven by means of fluorescence microscopy: by staining the aqueous phase using a water-soluble fluorescent dye it could be shown that the microvoids are initially formed by inclusions of the aqueous phase and not of organic solvents. These structures are not thermodynamically stable. They can be stabilized by removal of the organic solvents, which leads to “multiple secondary dispersions”. Structured polymer particles containing voids as described here could be interesting as white pigments, since they have the ability to scatter visible light.