Poly nanoparticle production

Microdevices may also be very effective and have also been proposed for nanoparticle production even if the flow is laminar, the very small size of the chaimel can allow very intensive mixing, but caution has to be taken because the small channels can be easily plugged [60,62]. However, two systems have been proposed and tested for particle precipitation one is based on the collision of microfragments [63], the other uses flow focusing in microfluidic channels to control nanoprecipitation of poly(lactic-co-glycolic acid)-b-poly(ethylene glycol) diblock copolymer as a model polymeric biomaterial for drug delivery [64]. 

The flash precipitation process, as stated before, was first employed for the production of poly(D,L-lactide) nanoparticles by Fessi et al. [41]. Polymer and drug were dissolved in an organic water-miscible solvent (acetone, tetrahydrofuran) and then the solution was infused into a large volume of water, where the solvent was dispersed quickly into the aqueous phase and stable nanoparticles were formed. As mentioned in the introduction, this process will be described in detail in this section, and in particular the interaction between the particle formation process and hydrodynamics will be discussed as the mixing efficiency is important, nanoparticles production by solvent displacement is often carried out in intensive mixers. 

Figure 8. Comparison between catalytic properties of Pt(poly-crystalline)/Al203 (Engelhard) and Pt(l 00)/Al203 (morphologically controlled Pt nanoparticles) the NO/CH4 reaction conversion (X) and yield (Y), and the reaction products at 500 °C.

Colloidal catalysts in alkyne hydrogenation are widely used in conventional solvents, but their reactivity and high efficiency were very attractive for application in scC02. This method, which is based on colloidal catalyst dispersed in scC02, yields products of high purity at very high reactions rates. Bimetallic Pd/Au nanoparticles (Pd exclusively at the surface, while Au forms the cores) embedded in block copolymer micelles of polystyrene-block-poly-4-vinylpyridine... 

Finally, these particles generated in ionic liquids are efficient nanocatalysts for the hydrogenation of arenes, although the best performances were not obtained in biphasic liquid-liquid conditions. The main importance of this system should be seen in terms of product separation and catalyst recycling. An interesting alternative is proposed by Kou and coworkers [107], who described the synthesis of a rhodium colloidal suspension in BMI BF4 in the presence of the ionic copolymer poly[(N-vinyl-2-pyrrolidone)-co-(l-vinyl-3-butylimidazolium chloride)] as protective agent. The authors reported nanoparticles with a mean diameter of ca. 2.9 nm and a TOF of 250 h-1 in the hydrogenation of benzene at 75 °C and under 40 bar H2. An impressive TTO of 20 000 is claimed after five total recycles. 

F. Karadas, G. Ertas, E. Ozkaraoglu, and S. Suzer, X-Ray-Induced Production of Gold Nanoparticles on a Si02/Si System and in a Poly(Methyl Methacrylate) Matrix, Langmuir 21, 437-442 (2005). 

This method, also known as the nanoprecipitation method, can be applied to numerous synthetic poly-mers. ° In general, the polymer is dissolved in acetone and the polymer solution is added into water. The acetone is then evaporated to complete the formation of the particles. Surface active agents are usually added to water to ensure the stability of the polymer particles. This easy technique of nanoparticle preparation was scaled up for large batch production. It leads to the formation of nanospheres. Nanocapsules can easily be prepared by the same method just by adding a small amount of an organic oil in the polymer solution.When the polymer solution is poured into the water phase, the oil is dispersed as tiny droplets in the solvent-non-solvent mixture and the polymer precipitates on the oil droplet surface. This method leads to the preparation of oil-containing nanocapsules... 

The properties of nanoparticles depend on surface morphology, specific surface area, particle size distribution, bulk density, drug incorporation, capacity, release, hydrophobicity, bioadhesiveness, and biodegradability. Nanoparticles (microspheres) loaded with the drug product can be formulated using copolymers, e.g., poly(lactide-co-glycolide) (PLG) or poly(lactide-co-ethylphosphate), by solvent extraction/evaporation technique. 

Elvassore N, Bertucco A, Caliceti P. Production of insulin-loaded poly (ethylene gIycol)/poly(lactide) (PEG/PLA) nanoparticles by gas antisolvent techniques. J Pharm Sci 2001 90(10) 1628-1636. 

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