Pickering Miniemulsion Polymerization Using Laponite Clay as a Stabilizer

Abstract

Solid-stabilized, or Pickering, miniemulsion polymerizations using Laponite clay discs as stabilizer are investigated. Free radical polymerizations are carried out using a variety of hydrophobic monomers (i.e., styrene, lauryl (meth)acrylate, butyl (meth)acrylate, octyl acrylate, and 2-ethyl hexyl acrylate). Armored latexes, of which the surfaces of the particles are covered with clay discs, are obtained, as confirmed by scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM). Overall polymerization kinetics of the Pickering miniemulsion polymerizations of styrene were investigated via gravimetry. Comparison with the bulk polymerization analogue clearly shows compartmentalization. Moreover, retardation effects up to intermediate monomer conversions are observed; they are more prominent for the smaller particles and are ascribed to the Laponite clay. A model is presented that allows for the prediction of the average particle size of the latexes produced as a function of the amounts of monomer and Pickering stabilizers used. It shows that under specific generic conditions the number of clay discs used correlates in a linear fashion with the total surface area of the latex particles. This is a direct result of the reversibility of the Laponite clay disc adhesion process under the emulsification conditions (i.e., sonication) used.

Physical Methods for the Preparation of Hybrid Nanocomposite Polymer Latex Particles

“…Bausch et al [83,84] showed that for large droplets onto which thousands of microspheres were assembled, this rule of 12 defects prevailed in the form of five-and seven-neighbor line defects, or grain boundary scars. Bon and coworkers [85] studied a system of intermediate size (tens to hundreds of particles on a sphere), i.e., the packing patterns of silica nanoparticles on polystyrene latex particles made via Pickering miniemulsion polymerization [86,87]. They found an excellent correlation between the experimental morphology and the nearest-neighbor distribution using metropolis Monte Carlo simulations, using a 12-24 Lennard-Jones potential.…”

“…Bon and coworkers [87] described the Pickering miniemulsion polymerization of styrene using Laponite RD clay discs as solids stabilizer in the absence of any auxiliary comonomer or surfactant. In a detailed mechanistic study [86], they reported that this Pickering miniemulsion polymerization using Laponite clay discs (ca. 25 nm in diameter and 1 nm in height) was successful and yielded armored polymer latexes for a variety of hydrophobic monomers, including styrene, lauryl(meth)acrylate, butyl(meth)acrylate, octylacrylate, and 2 ethylhexylacrylate.…”

Polystyrene/nano-SiO2 composite microspheres fabricated by Pickering emulsion polymerization: Preparation, mechanisms and thermal properties

“…So far, the preparation and forming principle of Pickering emulsion have been well documented by Binks and coworkers [15][16][17], Midmore [18], and Bon and coworkers [19,20] Moreover, a series of nanocomposite microspheres have been prepared. Bon and Colver [21] reported the fabrication of a variety of armored latex by Pickering miniemulsion polymerizations using Laponite clay discs as stabilizer. Zaragoza-Contreras et al [22] described the synthesis of carbon black/polystyrene conductive nanocomposite by Pickering suspension polymerization technique.…”

Design and fabrication of colloidal polymer nanocomposites

“…Then, emulsion polymerization [111,112] can be carried out to prepare polymeric nanocomposite particles, as presented schematically in Figure 12a. SEM images of laponite clay-armored polystyrene latex particles and montmorillonite clay-armored polyacrylamide latex particles are shown as further examples in Figures 12b [111] and 12c [113], respectively.…”