Polymer-microemulsion mixture

As the conversion to polymer proceeds, the micelles become progressively more and more swollen by the polymer-monomer mixture. As with other microemulsions, it eventually becomes problematic as to whether the resulting dispersed particles should be called micelles or swollen polymer particles with adsorbed surfactant. 

Polymerization of microemulsions that contains IL polar cores dispersed in a polymerizable oil has been reported for the system styrene/[C mim][BF ]/[MAUM][Br] where [MAUM][Br] is 1-(2-methyl acryloyloxyundecyl)-3-methylimidazolimn bromide and was used to stabilize [C mim][BF4]/styrene microemulsions [91]. In the same way, Texter and coworkers [92] use a ternary microemulsion formed by MMA/[C mim] [BF4]/[Cj2mim][Br] instead of an aqueous microemulsion for atom transfer radical polymerization showing that after the polymerization and isolation of the resultant polymers, the mixture of the catalyst and ILs (continuous phase and surfactant) can be recovered and reused improving the environmental sustainabihty of the processes. The rate of the polymerization process can be improved by using a new IL, BPYP-[MIM] PF, that combines properties of surfactants and catalyst hgands [93] (see Scheme 13.3). 

Corpart JM, Candau F (1993) Formulation and polymerization of microemulsions containing a mixture of cationic and anionic monomers. Colloid Polym Sci 271(11) 1055-1067... 

A reaction vessel was charged with styrene (1000 g), oleic acid (60.0 g), and dibenzyltrithiocarbonate (7.2 g) and then flushed with nitrogen. The mixture was next treated with an aqueous solution comprising water (4000 g), K2S2O8 (40.0 g), K3PO4 (40.0 g), and KOH (16.4 g), whereupon a fine microemulsion instantly formed. The reaction mixture was heated to 65°C where complete conversion to a stable, slightly yellow polystyrene latex was achieved in roughly 90 minutes solids comprised 20.6%. After workup the polymer had an M of 54,000 daltons with a PDI of 1.17. 

As mentioned previously, Reed and Carpenter (7) suggested that a two-phase mixture of an aqueous polymer solution and a microemulsion could be used to displace residual oil while simultaneously... 

The Interaction of water soluble polymers with microemulsions and with surfactants will, when the components are sufficiently concentrated, often result in a phase separation or change in the phase boundaries of the mixture as a function of external variables, such as temperature or salinity. In order to arrive at a better understanding of this technologically Important phenomenon, a series of experimental studies was carried out using a variety of water soluble polymers in conjunction with model mlcroemulslon systems. The polymers used Included polyethylene oxide, polyvinylpyrrolidone, dextran, xanthan, polyacrylamide, and hydrolyzed... 

The volume restriction effect as discussed in this paper was proposed several years ago by Asakura and Oosawa (12,13). Their theory accounted for the instability observed in mixtures of colloidal particles and free polymer molecules. Such mixed systems have been investigated experimentally for decades (14-16). However, the work of Asakura and Oosawa did not receive much attention until recently (17,18). A few years ago, Vrij (19) treated the volume restriction effect independently, and also observed phase separation in a microemulsion with added polymer. Recently, DeHek and Vrij (20) have reported phase separation in non-aqueous systems containing hydrophilic silica particles and polymer molecules. The results have been treated quite well in terms of a "hard-sphere-cavity" model. Sperry (21) has also used a hard-sphere approximation in a quantitative model for the volume restriction flocculation of latex by water-soluble polymers. 

Interesting effects are observed when a dispersion contains both larger and smaller particles the latter are usually polymer coils, spherical or cylindrical surfactant micelles, or microemulsion droplets. The presence of the smaller particles may induce clustering of the larger particles due to the depletion attraction (see Section 5.4.S.3.3, above) such effects are described in the works on surfactant-flocculated and polymer-flocculated emulsions. Other effects can be observed in dispersions representing mixtures of liquid and solid particles. Yuhua et al. ° have established that if the size of the solid particles is larger than three times the size of the emulsion drops, the emulsion can be treated as a continuous medium (of its own average viscosity), in which the solid particles are dispersed such treattnent is not possible when the solid particles are smaller. 

FIGURE 9.3 Interfacial tensions and solubilization parameters for microemulsions in a system containing a synthetic petroleum sulfonate, an alcohol cosurfactant, a mixture of refined oils, and NaCl brine. (From Reed, R.L. and Healy, R.N., in Improved Oil Recovery by Surfactant and Polymer Flooding, Shah, D.O. and Schechter, R.S., Eds., Academic Press, New York, 1977. With permission.)... 

The research on microemulsions currently concentrates on even more complex mixtures. By adding amphiphilic macromolecules the properties of microemulsions can be influenced quite significantly (see Chapter 4). If only small amounts of amphiphilic block copolymers are added to a bicontinuous microemulsion a dramatic enhancement of the solubilisation efficiency is found [27,28]. On the other hand, the addition of hydrophobically modified (HM) polymers to droplet microemulsions leads to a bridging of swollen micelles and an increase of the low shear viscosity by several orders of magnitude [29]. 

The enhanced oil recovery using solutions of surfactants or their mixtures has attained relatively little application. This is, first of all, due to the fact that surfactants adsorb from the solution on porous media of the reservoir, the specific surface of which may range from 150 to 3000 cmVcm, therefore, the use of emulsions, microemulsions and the so-called micellar-polymer flooding turned out to be more effective. In all of these processes, the flow... 

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