Emulsification comminution

There are a large number of methods (Table 2) to prepare nanoparticulate systems. These depend to a large extent on the material (polymer, protein, metal, ceramic) that will form the basis of the carrier. One can, in essence, consider three approaches to their production (0 by comminution (in the case of solids, milling, and in the case of liquids, high pressure emulsification) (ii) molecular self-assembly, such as that occurs with polymeric surfactants to form polymeric micelles or with dendrons to form dendrimeric aggregates and (iii) precipitation from a good solvent as shown in Figure 6. 

Emulsification by comminution (20-22) is very com-mon, the most widely used procedure for emulsion preparation. It can be earned out with very simple equipment, as for instance, a spoon in a bowl during the preparation of salad dressing in the kitchen for mixing water and oil. 

Finally, under well-defined conditions, it is possible to polymerize performed emulsion droplets. This is especially true for emulsions prepared by condensation methods where the conditions can be controlled in such a way that both secondary nucleation can be avoided and droplet or particle stability can be maintained during the entire polymerization. In the case of emulsions prepared by comminution techniques, suspension polymerization is a good example of a system where the (conditions) properties of emulsions can be converted into the corresponding properties of sols/suspensions. For smaller drop sizes, the solubility of the monomer in water is crucial, but unfortunately, very hydrophobic monomers are technically unimportant, at least nowadays. The addition of hydrophobic molecules needs tailored emulsification procedures regarding and DSD, and a certain maturation time to result in stable emulsions. Miniemulsion polymerization is a promising way, although the question as to what extent a 1 1 copy of an emulsion is possible is still waiting for an answer. 

The comminution of liquid phases is a special case of the above and is generally referred to as emulsification. Because of the nature of liquid systems, emulsification has a number of additional variations not generally available for the formation of dispersions. These include spontaneous emulsification, electroemulsification, and spontaneous microemulsion formation. 

The concept of energy density relies on the experimental finding that power density and dispersion time affect the resulting mean particle size in a similar manner it applies to emulsification too (Karbstein and Schubert 1995 Schuchmann and Danner 2004). Besides this, it is in accordance with the classical laws of comminution, which correlate the change in particle size to the energy input per unit mass of solid (Richardson and Harker 2002, pp. 100-102). 

Dispersion methods. In this case one starts with preformed particles of the bulk chemical, which are then subdivided into smaller partides by a suitable dis-persion/comminution process. An example of this method is the production of suspensions by wet milling (using grinding equipments). Emulsification of oils (using high speed stirrers or homogenisers) is also a kind of dispersion method. 

The most common size reduction processes, comminution, emulsification, and spraying, share several common features. Eggers and ViUermaux discuss... 

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