Emulsion FRRPP

Controlled free-radical polymerization (CFRP) has been used successfully to produce block, graft, and other controlled architecture copolymers within the last decade for a variety of free radically polymerizable monomers. The main techniques include reversible addition fragmentation and transfer (RAFT) polymerization, stable free-radical polymerization (SFRP) mediated by nitroxide/alkoxyamine based radicals, atom transfer radical polymerization (ATRP), diphenyl ethylene (DPE) mediated polymerization, and novel precipitation/emulsion polymerization based methods like free-radical retrograde precipitation polymerization (FRRPP). ... 

The FRRPP can also be implemented in suspension and emulsion polymerization processes. Its analysis in suspension system has turned out to be straightforward, because the suspension size scale (mm sizes) does not interfere with the reaction mechanism, even if one includes mass and thermal transport effects. In emulsion polymerization systems, the submicron size scale of emulsion particles interfere with thermal and probably mass transport effects in the system. Also, the hydrophobic portions of surfactant molecules could affect the phase equilibrium aspects of the FRRPP system. 

A redox system is normally used for emulsion FRRPP. For first-stage polymerization of S in ether, three mixtures were prepared. 

Fig. 3.2.3 Conversion-time plot for emulsion FRRPP of S in ether at 80°C and 70 psig...

The final product was elastic and self-tacking white solid. Upon dissolution in THF and drying, the solid was ttanslucent, indicating a block copolymer structure. Particle size analysis of the latex is shown in Fig. 3.2.4 to have a multimodal distribution, ranging from submicron to 10 p,m or greater, but still a stable enough emulsion. In fact, all of our latex products made from this type of emulsion FRRPP... 

Fig. 3.2.5 Picture of a PS-PBA block copolymer emulsion and solid product made from a multistage FRRPP process with emulsification of the first-stage product...

Aside from the PS-PBA type of emulsion FRRPP product introduced in Section 3.2, it is worth mentioning the promise of the formation of other emulsion FRRPP block copolymer products, such as PMMA-PBA. 

Aside from the coatings that can be produced from emulsion FRRPP (Section 3.2.3), this section contains other materials that were developed for more specialized... 

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