Inverse emulsion polymerization discussion

The mechanical stability of polymers was related to the polymer s conformation in some of the earlier drag-reduction studies. Above a critical stress, degradation was faster the more contracted and entangled the polymer s conformation (5-7). In petroleum applications the mechanical instability of synthetic relative to carbohydrate polymers was well-recognized. The relative stability problems (possibly related to DUEVs (8)) encountered in the use of high molecular weight hydrolyzed poly(acrylamide) (HPAM) led to the development of an inverse-emulsion polymerization technique (9). (Current research directions using this technique are discussed in Chapter 9.)... 

The present review will mainly focus on inverse emulsion polymerization, the most commonly employed water-in-oil synthesis method and on inverse microemulsion polymerization which is more recent and offers some new prospects. The formulation components and their actions, the various structures of the colloidal dispersions prior to polymerization and some latex properties will be discussed. The kinetics and the mechanisms occurring in these water-in-oil systems will also be analysed and compared to the more conventional emulsion polymerization process. 

Recently, a number of groups have also reported the Pickering stabilization of monomer-containing lipid droplets by clays, and their subsequent free radical polymerization [291]. As these articles fall outside the scope of this review, they will not be discussed further. Although not strictly speaking in the scope of the present review, it is also worth mentioning the recent work of Voorn et al. on the first surfactant-free inverse emulsion polymerization stabilized with hydrophobic MMT platelets [292],... 

Due to the hydrophilic nature of nascent clays, one may envisage that hydrophilic clays can be encapsulated by inverse emulsion polymerization. As discussed in Section 3.2, in a direct emulsion containing hydrophilic clays, clays may be predominately located in the continuous aqueous phase and some may reside at the surface of the micelles (forming a Pickering-type emulsion in the presence or absence of surfactants) after polymerization, armored particles with clay covering the particles have been commonly observed (Figure 3.2a). 

In order to overcome the difficulties associated with inverse emulsion and dry polymers, Nalco has become involved in the development and commercial practice of a unique technology for the manufacture of high molecular weight water soluble polymers based on acrylamide. This polymerization process permits the manufacture of these extremely useful polymers as water continuous dispersions. The polymer products are liquid, and so retain the virtues of ease and safety of handling, but they are manufactured in water instead of in a hydrocarbon and surfactant matrix. Thus, no oil or surfactants are released to the environment with the application of these polymers. The performance of these polymers in the various end use applications is equivalent to, or in some cases exceeds, that obtained with similar polymers produced in inverse emulsion or dry form. A discussion of this dispersion polymerization technology, the monomers and their polymers, the stabilizer polymers, particle characteristics, viscosity considerations and the thermodynamic and physical stability of the products constitutes the subject of this manuscript. 

Surface-active materials are used to stabilize dispersions in industrial applications when coalescence must be prevented, as for suspension and emulsion polymerization processes. Concentrated dispersions are more likely to undergo phase inversion. This complex coalescence-dominated phenomenon is discussed later in this section. 

Dispersions may also be formed by the continuous addition of one phase into another under agitation conditions. This method offers a safe procedure for handling exothermic reactions such as nitration and emulsion polymerization. The amount of phase addition will determine if phase inversion occurs as discussed in Section 12-5.4. 

By integrating CNTs with PANi nanofibers, high density and high-suiface areas are possible that can lead to improvements in the conductivity and the development of electronic devices with superior properties [78]. The composites of PANi-CNT can be synthesized by various methods such as electrochemical processing, surfactant free aqueous polymerization, micelle-CNT hybrid template directed synthesis, inverse emulsion pathways, interfacial polymerization, plasma polymerization, in-situ and ex-situ polymerization. The details of these methods have been discussed by Oueiny et al. [8]. In-situ polymerization is one of the most important methods developed so far to integrate CNTs and polyaniline. Polymerization methods include stirring, static placement, sonication and emulsion polymerization [78]. 

In this study, after a brief introduction to PI we provide the bases of a technique for the preparation of polymeric micro-porous materials, known as polyHIPE polymers (PHPs) which are now used extensively in PIM, and micro-reactor technology. These polymers are prepared through the high internal phase emulsion (HIPE) polymerization route. In order to control the pore size, the flow-induced phase inversion phenomenon is applied to the emulsification technique. The metalization of these polymers and formation of nano-structured micro-porous metals for intensified catalysis are also discussed. Finally, we illustrate the applications of these materials in chemical- and bioprocess intensifications and tissue engineering while examining the existence of several size-dependent phenomena. 

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