Preparation of polyacrylamide latexes by concentrated emulsion polymerization

Abstract

A concentrated emulsion is a gel-like emulsion whose internal phase ratio is greater than 0,74 (which is the volume fraction of the most compact arrangement of spheres of equal size). In this type of emulsion'-3), the dispersed phase is composed of polyhedral cells separated by thin films of the continuous phase. In contrast, the conventional (dilute) emulsions consist of a small volume fraction of dispersed droplets, a continuous phase, and micellar aggregates of surfactant molecules. The repulsive forces between the surfactant molecules adsorbed on the surface of neighboring cells are responsible for the stability of the concentrated emulsions. The shape and the size of the latex particles in the concentrated emulsions remain relatively unchanged during polymerization, while the polymer latex particles grow in the conventional emulsion polymerization. Consequently, the present approach could provide a new avenue for the control of the size of the polymer latexes. In a previous paper4), the polymerization of the hydrophobic monomer styrene, dispersed in water, with an internal phase ratio as high as 0,96, was reported. Compared to bulk polymerization, both higher molecular weights and higher rates of polymerization were observed.In the present note, we report the concentrated emulsion polymerization of the hydrophilic monomer, acrylamide, dispersed in decane with an internal phase ratio of 0,94. Compared to the conventional inverse emulsion polymerization5), a much smaller amount of organic solvent is employed to produce the polymer latexes.

Encapsulation of inorganic particles via miniemulsion polymerization. III. Characterization of encapsulation

“…Ruckenstein et al used concentrated emulsion polymerization for the encapsulation of submicron-size alumina and fumed silica particles with crosslinked acrylamide. 14,15 Dispersion polymerization was also employed for encapsulation of submicron size silica particles within different polymer particles such as polystyrene, 16,17 polyaniline, 18 and polypyrrole. 19 All encapsulation studies revealed that the successful encapsulation of a pigment first requires a good dispersion of the inorganic particles in the medium prior to carrying out the polymerization.…”

Preparation of macroporous hydrophobic materials filled with aligned porous hydrophilic domain via emulsion‐templated and unidirectional freezing technique

“…The viscosity of aqueous phase increased with an increase of PVA concentration, which made it difficult to be dispersed and therefore gained larger droplets diameter. Moreover, PVA is often used as the hydrophilic stabilizer in oil‐in‐water emulsion; as a result, the increasing PVA concentration can reduce the stability of W/O HIPE and enhance droplet coarsening at the polymerization temperature …”

“…Moreover, PVA is often used as the hydrophilic stabilizer in oil-in-water emulsion; as a result, the increasing PVA concentration can reduce the stability of W/O HIPE and enhance droplet coarsening at the polymerization temperature. [33] For low PVA contents (i.e. 1wt%), the SEM images ( Fig.…”

Synthesis of Acrylonitrile Based High Internal Phase Emulsion Monoliths and their Application in Recovery of Heavy Metal Ions

“…Lissant described the structure and properties of the non-Newtonian, thixotropic Bingham fluids termed as high internal phase emulsions (or high internal phase ratio emulsions, HIPREs) [2][3][4]. These emulsions have also been referred to as concentrated emulsions [5][6][7], gel emulsions [8][9][10], and hydrocarbon gels [11]. The resulting porous polymers formed have three dimensional porous structure with formation of cells of different morphologies [12][13][14].…”