Pickering Miniemulsion

One of the main disadvantages of the MMT Pickering miniemulsions approach is the low stability of the dispersion for long storage times and the low solids content achieved so far.  

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Bon, Keddy, and coworkers [109] demonstrated that soft armored polymer latex made via Pickering miniemulsion polymerization [i.e., poly(lauryl acrylate) armored with Laponite clay discs] could be used as a nanocomposite additive in standard poly(butyl acrylate-co-acrylic acid) waterborne pressure-sensitive adhesives (PSAs), leading to marked mechanical property enhancements (see Fig. 13). 

Voorn and coworkers demonstrated the inverse Pickering miniemulsion polymerization of aqueous acrylamide and 2-hydroxyethyl methacrylate in cyclohexane using hydrophobically modified Montmorillonite platelets (cloisite 20A) as solids stabilizer [110]. 

The use of a high-energy homogenization step to prepare the submicrometer-sized monomer droplets for the Pickering miniemulsion process could be a drawback for industrial scale-up. A better outcome could be achieved by the equivalent emulsion polymerization process in which solid nanoparticles were used as solids stabilizer. 

Bon SAF, Colver PJ (2007) Pickering miniemulsion polymerization using Laponite clay as a stabilizer. Langmuir 23(16) 8316-8322... 

The Pickering miniemulsion polymerization was successfully extended to other monomers including butyl methacrylate, 2-ethylhexyl acrylate and lauryl methacrylate. It appeared that these hydrophobic monomers showed more success than partially water-misdble monomers such as methyl acrylate or... 

Waterborne acrylic-clay nanocomposite PSAs have been synthesized by suspension polymerization, emulsion polymerization and Pickering miniemulsion polymerization of a soft acrylate monomer in the presence of clay, which was followed by blending the polymer-clay nanocomposite particles with a standard acrylate latex for application as a waterborne PSA. ... 

Wang et al. succeeded in preparing waterborne PSAs with nanostructured features that ean build in an energy dissipation mechanism without stiffening the structure too much. In their study, soft-hard polymer particles having Laponite clay armor were synthesized by the Pickering miniemulsion polymerization of -lauryl acrylate (LA). The resulting poly(lauryl acrylate) (PLA)-Laponite hybrid particles were then blended at various low concentrations with... 

Bon and Colver showed that the surface location of clay influenced the overall polymerization kinetics and Pickering miniemulsion polymerizations of styrene in the presence of clay showed compartmentalization. Moreover, retardation effects up to intermediate monomer conversions were observed they were more prominent for the smaller particles and were ascribed to the Laponite clay. 

Polymerization of Emulsion Droplets Armored with Inorganic Nanoparticles Pickering Suspension and Miniemulsion... 

Cauvin S, Colver PJ, Bon SAF (2005) Pickering stabriized miniemulsion polymerization preparation of clay armored latexes. Macromolecules 38(19) 7887-7889... 

Inverted raspberry-like morphologies (the mineral particles being located at the surface of the latex spheres) have also been discussed in Sections 4.4.2.2 and 4.4.2.4 about colloidal silica and layered silicates, respectively. These are mainly a consequence of the surfactant-like behavior of the inorganic particles in specific situations. This was clearly illustrated in a recent report by Landfester, who showed that silica or clays can be used as pickering stabilizers of miniemulsion jxjlymer-izations, resulting therefore in the formation of armored latexes, the surface of which was recovered by the small inorganic particles [99,131]. 

Without additional surfactant, the emulsion could not be stabilized solely be the ricinoleic acid and phase separation occurred. The coalesced monomer phase was loaded with magnetite particles, showing that the phase transfer of magnetite was successful (see Fig. 18). With additional surfactant, a stable miniemulsion resulted. TEM images of the composite parties after polymerization however revealed that the magnetite particles were located at the polymer particle interface and inhomogeneously distributed (see Fig. 18). Presumably pickering emulsions... 

Pickering Suspension and Miniemulsion Polymerizations a Brief Overview... 

Over a century ago, Ramsden and Pickering observed that colloidal particles located at the oil/water interface were able to stabilize emulsions of both the oil-in-water and the water-in-oil type. These emulsions are referred to as either Pickering emulsions or solid-stabilized emulsions. In line with these concepts, the polymer community has recently shown a surge of interest in the production of a vast range of hybrid colloidal materials using various nanoparticles as solid stabilizers for miniemulsion or suspension polymerization. 

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