Aqueous miniemulsions

It was shown that the principle of aqueous miniemulsions could be transferred to non-aqueous media [45]. Here, polar solvents, such as formamide or glycol, replace water as the continuous phase, and hydrophobic monomers are miniemulsified with a hydrophobic agent, which stabilizes the droplets against molecular diffusion processes. It turned out that steric nonionic surfactants based on poly(ethylene oxide) tails are far more efficient than ionic stabilizers,... 

Ethylene can be polymerized using an aqueous miniemulsion consisting of an organo-transition metal catalyst at ethylene pressures of 10-30 bar and temperatures of 45-80°C resulting in large particles of about 600 nm [129]. A maximal productivity of 2520 kg PE per g atom active metal was achieved, which represents about 60% of the productivity of the same catalyst when used in ethylene suspension polymerization in organic phase. 

Interestingly enough, this process is effective in bulk, in water suspension and in aqueous miniemulsion . The long-lived propagating species can be derivatized into a series of functional groups by addition of properly substituted nitroxides or nonpolymerizable olefins". Moreover, PVac-fc/oc -PS diblock copolymers were synthesized successfully, which is an additional step in the macromolecular engineering of PVac. ... 

Anionic polymerization in non-aqueous miniemulsions for polyamide nanoparticles [12], and in aqueous phase for polybutylcyanoacrylate (PBCA) nanoparticles [13]... 

Aschenbrenner EM, Weiss CK, Landfester K (2009) Enzymatic esterification in aqueous miniemulsions. Chem Eur J 15 2434-2444... 

Barrere M, Landfester K (2003) High molecular weight polyurethane and polymer hybrid particles in aqueous miniemulsion. Macromolecules 36 5119-5125... 

Crespy D, Landfester K (2009) Synthesis of polyvinylpyrtolidone/silver nanoparticles hybrid latex in non-aqueous miniemulsion at high temperature. Polymer 50 1616-1620... 

Barrere, M. and K. Landfester, Polyester synthesis in aqueous miniemulsion. Polymer 44 (2003) 2833-2841. 

The catalytic polymerization of butadiene with a cobalt catalyst was performed, producing particles of 150-200 nm diameter that consisted of crystalline 1,2-polybutadiene [80]. Metathesis polymerization reactions in aqueous miniemulsion were carried out when water-resistant metathesis catalysts became available. 

The use of water-containing miniemulsions (as described above) is Hmited to particular monomers for anionic polymerization. Since, in many cases, the initiator and active species are sensitive to water, the polymerization caimot be carried out in either water-in-oil or oil-in-water miniemulsions. The anionic polymerization of e-caprolactam in a non-aqueous miniemulsion was first reported in 2005 [103]. As the e-caprolactam monomer is hydrophilic, it was necessary to conduct the polymerization in an inverse miniemulsion. Unfortunately, the molten e-caprolactam-in-oil miniemulsions could not be stabilized efficiently, in contrast to dimethyl sulfoxide (DMSO)-in-oil miniemulsions. Therefore it was necessary to dissolve the e-caprolactam directly in DMSO, to form the dispersed phase. This synthetic strategy, which permitted the production of polyamide-6 nanoparticles, paved the way for a variety of water-sensitive reactions to be performed in miniemulsion nanodroplets, including the creation of hydrophihc polyurethane capsules and particles (see below). Subsequently, poly(e-caprolactone)... 

Cross-coupling reactions were carried out in direct aqueous miniemulsions with 1,2,4-tribromobenzene as crosslinker, and Pd as catalyst [147], in order to obtain aqueous latexes of crosslinked poly(p-phenylene ethynylene) with good optoelectronic properties. The Glaser couphng reaction was also used to synthesize fluorescent conjugated particles of poly(arylene diethynylenes) in direct miniemulsions [148]. For this, 4,4 -dinonyl-2,2 -bipyridine was found to be a suitable ligand for solubilizing the copper (I) chloride catalyst in the toluene droplets. In this case, a solution of the monomers in toluene was first mixed with the solution of the catalyst, and the resultant mixture then miniemulsified in an aqueous solution of cationic surfactant. 

Farcet et al. [88,89] reported that using SGI nitroxide as a mediator, the monomer nBA could be successfully performed in batch aqueous miniemulsion at 112 °C under 3 bars pressure. Different MWs were targeted and in all cases, the Mn increased linearly with monomer conversion, matching the predicted value and the poly-dispersity was narrow. For example, a of up to 5 x 10 g / mol could... 

Aqueous miniemulsion polymerization of styrene was performed in the presence of CeFis-I as CTA, yielding particles with a good control of the molecular weights, in contrast to emulsion polymerization where the transfer agent efficiency was low due to a slow diffusion of the hydrophobic perfluor-ohexyl iodide from the monomer droplets to the active particles during polymerization.The chains were capped with iodine as evidenced by the successful chain extension upon addition of butyl acrylate. The miniemulsion process was also successfully applied to the preparation of triblock copolymers PS-b-PDMS-b-PS starting from a telechelic diiodo-poly(dimethylsiloxane) macrotransfer agent. A somewhat similar procedure was used to prepare PVAc-b-PDMS- -PVAc triblock copolymers, but the polymerization was performed under UV irradiation (instead of thermal initiation) and in the absence of radical initiator. In this case, the aqueous dispersion medium was a key parameter to achieve a controlled polymerization (Scheme 19). ... 

Scheme 19 Polymerization of VAc in the presence of an iodinated macrophotoiniferter in aqueous miniemulsion.

Lefay C, Nicolas J (2010) ControlledAiving radical polymerization in aqueous miniemulsion. In Mittal V (ed) Miniemulsion polymerization technology. Wiley, Hoboken, pp 173-210... 

Several reviews cover the considerable progress of NMP and other CRP techniques in aqueous miniemulsion or emulsion polymerizations. Preparation of hybrid latex particles and core-shell particles in aqueous media using NMP was summarized by Charleux et... 

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