Colloidal polymer dispersions, miniemulsion

Miniemulsion polymerization is advantageous for the production of complex colloidal polymer dispersions since, due to droplet nucleation, no mass transfer through the aqueous phase is needed. Therefore, it allows the synthesis of a broad range of materials not obtainable by the means of... 

Other Components. The smaller the particle size, at a given phase ratio, the more difficult it is to ensure colloidal stability (cf Fig. 5). This means that for aqueous heterophase polymerizations in the order suspension < microsuspension < emulsion < miniemulsion < microemulsion, the stabilizer concentration increases. Contrary to the simple polymerization of st5Tene in water, polymerization recipes for industrially important polymer dispersions comprise up to six monomers, frequently more than two emulsifiers, more than one initiating system, and a few other aids like biocides, defoaming agents, plasticizers for supporting film formation (39). The monomer-to-water ratio is adjusted in such a way that a solid content results typically between 40 and 60% or even higher. The amoimts of surfactants and initiator (mainly peroxodisulfate) are typically between 0.5 and 2% (w/w) relative to the monomers and 0.5% (w/w) relative to water, respectively. 

In many cases, the reported polymer syntheses in miniemulsion were performed via free-radical polymerization. The polydispersity of the miniemulsion particles and the dispersity of the polymer are not directly correlated, and for many appHcations attention is focused on the colloidal properties in terms of their size, their size distribution, and the morphology of the nanoparticles themselves. Typically, the polymer s chemical characteristics (including its architecture) are of less interest. 

A rather different approach to utilize surface effects for the orientation of smectic elastomers is radical crosslinking of Uquid crystalline polymers using a dispersion or miniemulsion technique in a mixture of solvent and surfactants. CrossUnked smectic-A colloids were prepared in sizes of 100-200 nm showing highly oriented phase structures that could be visualized directly in transmission electron microscopy [107]. 

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