Stable nanoparticles, synthesis problems

One of the main problems in modern nanotechnology is the preparation and stabilization of nanoparticles of different nature semiconductors, metals, organic compounds, etc. Nowadays there are a number of methods for nanoparticle synthesis [1]. Among them water-in-oil reverse micelles (RMs) are the successful technique for the controlled preparation of very small and monosized nanoparticles. Water-in-oil RMs are thermodynamically stable dispersion of nanosized water drops in organic solvent, stabilized by surfactants. RMs are formed spontaneously due to the surfactants, which diminish the interface tension down to ultralow values, and as a result the free energy decreases when the total oil-water interfacial area increases. Thermodynamically stable water-in-oil microemulsions can be produced at strictly defined conditions. It is possible to change the size of the water pool of RMs by variation of the ratio between water and surfactant concentrations. This allows changing the size of nanoparticles, which are stabilized in such microemulsions. 

Microemulsion polymerisation has shown a great advantage over conventional polymerisation strategies such as emulsion polymerisation with respect to the end particle size, polydispersity and reproducibility of the product characteristics. Although we still face severe problems regarding the polymerisation of microemulsions (see Section 11.2 in Chapter 11), it has been employed for the synthesis of polymeric nanoparticles of pharmaceutical interest. Microemulsion polymerisation involves free-radical polymerisation in a large number of monomer-swollen microemulsion droplets and represents a thermodynamically stable, transparent one-phase reaction system. Generally, the microemulsion droplet is considered as initiation locus for the polymerisation. The type of microemulsion used for the polymerisation depends on the monomer properties [148]. 

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