Applications small-molecule emulsifiers

One of the most straightforward applications of polymer particles generated by MF methods includes the encapsulation and delivery of small molecules such as drugs, nutrients, food, or cosmetics ingredients. As explained in Section 8.4.2.1, an ingredient to be encapsulated is dissolved or dispersed in the dispersed phase, the mixture is emulsified, and a precursor droplet is transformed into a polymer particle. This approach has been demonstrated for uniformly gelled core-shell microgels derived from compound droplets [48]. 

In order to synthesize an interfacial polyelectrolyte the ionizable groups must be chemically bound to the interface and be an integral part of the polymer molecules comprising the colloidal particles. It is preferable to avoid adsorbed emulsifier, which is usually employed to stabilize these colloids, as it complicates the subsequent purification and quantitative surface characterization of the system. Thus the classical technique of emulsion polymerization, as described by Harkins [2], is not applicable. The systems are actually simpler, employing only monomer(s), water and initiator. It is most important that the initiator be very soluble in the water and that it form ionizable free radicals. The monomer must have a finite solubility in water, although this may be very small (even styrene satisfies this requirement at 0.038 wt.%), but may be present in amounts far in excess of this as an initially separate phase. Initiation of polymerization must then occur in the aqueous solution. For instance, if the initiator is potassium persulfate, K2S2O8, free radical-ions are formed (along with some OH) by the thermal decomposition of the anion ... 

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