Number, microdroplets

Beaded polymeric supports are produced by a two-phase suspension polymerization in which microdrops of a monomer solution are directly converted to the corresponding microbeads. The size of a microdroplet is usually determined by a number of interrelated manufacturing parameters, which include the reactor design, the rate of stirring, the ratio of the monomer phase to water, the viscosity of both phases, and the type and concentration of the droplet stabilizer. 

Ion traps have been used in a number of studies of optical properties of microdroplet lasers14,15 and the ion trap itself can be used as a useful mass spectrometer for fundamental studies of trapped particles and micrometer to nanoscale aerosols16. 

This technique is very similar to solution polymerisation except that the monomer is suspended rather than dissolved in an inert liquid, often water. Heat transfer and reduction in viscosity are comparable with those of solution polymerisations, though mechanical agitation and the presence of suspending agents are necessary to maintain the monomer in suspension. Effectively the technique works because there are a large number of microdroplets undergoing bulk polymerisation. 

When a mixture of water, monomer, surfectants, initiator, and property control agents forms microdroplets of monomer in water with dimensions of 1 pm, an emulsion has been formed (8). If polymerization occurs in the 1 pm droplets by migration of an initiator active site from the aqueous phase to the microdroplet to completely react the droplet, the process is emulsion polymerization. A major problem in emulsion polymerization is developing a mixture which remains a stable emulsion throughout the polymerization. Polymerization kinetics is controlled by the number of microdroplets in the reaction mixture and the polymerization rate of the monomer. Polymer can be recovered as fine particles fiom the completed reaction but is most often used as the emulsion of polymerized product. Emulsion polymerization is commonly used to synthesize two polymer types covered in this book, polyvinyl chloride... 

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