Radical-initiated polymerization in heterogeneous media

Owing to the broad interest of such particles not just for specialty applications, a huge amount of work has been developed in order to elaborate surface functionalized latex particles. In that purpose, it is possible to deal with the use of molecular or macromolecular species (bearing the functionality) along with the polymerization protocol (batch, semi-continuous, core-sheU, shot-growth etc.) (Pichot, 1995 Pichot Delair, 1999). 

Regarding the first point, it is out of scope here to describe all various strategies since many recent reviews already provided useful and detailed information. Table 10.2 summarizes the main approaches which can be followed. 

The production of such particles usually results fi-om the emulsion copolymerization of a hydrophobic monomer, such as styrene with a water-soluble monomer, such as acrylic acid. Differences in water solubility of the two monomers along with disparate reactivity ratios led to the preparation of particles having a core-shell structure with the hydro-phobic polymer in the core and the water-soluble polymer in the shell layer. It was also found that precipitation polymerization of alkyl(meth)acrylamide, such as N-isopropyl 

Origin of surface functional groups Chemical structure Surface groups References 

Initiator-derived Persulfate salts ROSO3, M+, ROH, RCOOH Goodwin et al. (1978) 

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Polymer latex nanoparticles can be prepared in many materials such as polystyrene and acrylate with controllable size, through radical-initiated polymerization in heterogeneous media (Figure 14.2). The sizes of latex nanoparticles are very dependent on the polymerization conditions. To yield nanosized particles, the polymerization is usually carried out in miaoemulsions [34], For some applications, two or more monomers are used. For example, for polystyrene nanoparticles, divinylbenzene (DVB) is used as a cross-linker to improve the structural performance [35] and methacrylic acid (MAA) or methacrylate (MMA) is used as a co-monomer to provide the nanoparticles with desirable surface chemistry [36,37], Furthermore, some fluorochromes or magnetic materials are incorporated into polymer nanoparticles, to render the particles multifunctional [38,39],... 

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