Microemulsion polymerization inverse

Manufacturing processes have been improved by use of on-line computer control and statistical process control leading to more uniform final products. Production methods now include inverse (water-in-oil) suspension polymerization, inverse emulsion polymerization, and continuous aqueous solution polymerization on moving belts. Conventional azo, peroxy, redox, and gamma-ray initiators are used in batch and continuous processes. Recent patents describe processes for preparing transparent and stable microlatexes by inverse microemulsion polymerization. New methods have also been described for reducing residual acrylamide monomer in finished products. 

Inverse least squares, 539-41 Inverse micelles, 25487 Inverse microemulsion polymerization, 20 461... 

The general features of inverse microemulsion polymerization at the present state of knowledge are presented. The influence of various water-soluble monomers on the structural properties of the... 

In this paper, we review the main results obtained so far in the field of inverse microemulsion polymerization. The role played by the monomers on the structural characteristics of the microemulsion prior to polymerization will be emphasized. The main properties of the final latices will be discussed in light of both basic and applied research. 

The novel process of inverse microemulsion polymerization allows one to prepare microlatices with characteristics... 

The main features of inverse microemulsion polymerization process have been reviewed with emphasis given to a search for an optimal formulation of the systems prior to polymerization. By using cohesive energy ratio and HLB concepts, simples rules of selection for a good chemical match between oils and surfactants have been established this allows one to predict the factors which control the stability of the resultant latices. The method leads to stable uniform inverse microlatices of water-soluble polymers with high molecular weights. These materials can be useful in many applications. 

A growth in micellar size is always observed during the reaction due to the internal dynamics of microemulsions and inverse-microemulsions. This takes the form of either coagulation of active and inactive micelles or the diffusion of monomer from the unreacted micelles to the nucleated particles. Each final particle contains a number of macromolecules, on the order of one, in a collapsed state [33], with the particle size independent of the nature of the free radical initiator [34]. These features lead to a unique kinetic mechanism relative to the other heterophase polymerizations discussed herein [33, 35,36]. A more detailed discussion of microemulsion and inverse-microemulsion polymerizations are given in two recent reviews [37, 38]. 

Inverse-suspension, inverse-emulsion and inverse-microemulsion polymerizations should be developed independently as has been the precedent for oil-inwater polymerizations. This includes explicitly considering the unique chemistry of various emulsifiers, organic phases, monomers and initiators. Furthermore, the chemical and colloidal models for each of the three water-in-oil polymerizations will be specific to a given type of organic phase and a restricted family of emulsifiers. 

The utility of microemulsion polymerization comes from its capability of producing smaller particles than those obtained by emulsion polymerization and of forming porous solid materials (by inverse microemulsion polymerization). This process has also been found to be suitable for performing CRP [206]. More particularities on microemulsion polymerization can be found in References 188, 204, 207, and 208. 

Nanostmctured Template Method HCl-doped PANI-NFs having a long nanosize fibril stmcture have been prepared by an inverse microemulsion polymerization process using... 

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. 

While inverse (mini)emulsion polymerization forms kinetically stable macro-emulsions at, below, or around the CMC, inverse microemulsion polymerization produces thermodynamically stable microemulsions upon further addition of emulsifier above the critical threshold. This process also involves aqueous droplets, stably dispersed with the aid of a large amount of oil-soluble surfactants... 

Fernandez, V.V.A. Tepale, N. Sanchez-Diaz, J.C. Mendizabal, E. Puig, J.E. Soltero, J.F.A. Thermoresponsive nanostruetured poly(N-isopropylacrylamide) hydrogels made via inverse microemulsion polymerization. Colloid Polym. Sci. 2006, 284 (4), 387-395. 

Juranicova, V. Kawamoto, S. Fujimoto, K. Kawaguchi, H. Barton, J. Inverse microemulsion polymerization of acrylamide in the presenee of N,N-dimethylacrylamide. Angew. Makromol. Chem. 1998,258 (1), 27-31. 

Preparation of iron oxide magnetic nanoparticles and their encapsulation with polymers in W/0, i.e. inverse microemulsion polymerization, was also applied by O Connor et al. [167]. Inverse microemulsion polymerization was used to prepare submicron hydrophilic magnetic latex containing 5-23 wt% iron oxide. AM and crosslinker MBA were added to an aqueous suspension of previously synthesized iron oxide nanoparticles (6 wt%) this aqueous phase was dispersed in a aerosol OT (sodium l,4-bis(2-ethylhexoxy)-l,4-dioxobutane-2-sulfonate) (AOT)-toluene solution to form a W/O microemulsion, followed by polymerization with AIBN or V-50 as initiator. The particle size (80-180nm)was controlled by tuning the concentration of the water-soluble crosslinker agent as well as the amount of surfactant with respect to water [168]. 

The use of microlatices for biological applications is also very attractive. Let us recall that conventional latices prepared from emulsion polymerization are already used for such purposes, for example, in immunoassays, as adsorbents for proteins, for immobilization of enzymes and antibodies, and for controlled release in drug delivery [165]. The latex particle size is in the range 0.1-10 /im. Stable microlatices in the nanosize range (20-30 nm) may be preferred, and some procedures based on inverse microemulsion polymerization have been proposed for the preparation of nanocapsules [4,166-169]. 

Microemulsion polymerization [114] involves the polymerization of oil-in-water and water-in-oil monomer microemulsions. Microemulsions are thermodynamically stable and isotropic dispersions, whose stability is due to the very low interfacial tension achieved using appropriate emulsifiers. Particle nucleation occurs upon entry of a radical into a microemulsion droplet. Microemulsion polymerization allows the production of particles smaller than those obtained by emulsion polymerization. This leads to a higher number of polymer particles, which results in a more compartmentalized system. Under these conditions, the life-time of the polymer chains increases leading to ultra-high molecular weights. Inverse microemulsion polymerization is used to produce highly efficient flocculants. 

Daubresse, C., C. Grandfils, R. Jerome and P. Teyssie, Enzyme immobilization in nanoparticles produced by inverse microemulsion polymerization, yottma/ of Colloid and Interface Science, 168 (1994) 222-229. 

J. H. Barajas, Inverse-Emulsion and Inverse-Microemulsion Polymerization of Acrylic Water Soluble Monomers, Ph.D. Thesis, Vanderbilt University, 1996, Chapt. 4 . 

Several methods have been reported in the scientific literature for the synthesis of microgel particles. These include emulsion polymerization (5), inverse microemulsion polymerization (6,7), and anionic copolymerization (8) (see Heterophase Polymerization). 

Polymerization of 0/W microemulsions is referred to as microemulsion polymerization and that of W/0 microemulsions as inverse microemulsion polymerization. Both of them proceed in a similar manner. The radicals are produced in the continuous phase and react with the monomer dissolved in the continuous medium. Once they become surface active, they are able to enter into the monomer-swollen micelles, which become polymer particles [102,103]. 

Inverse microemulsion polymerization is used for the production of water-soluble polymers of high molecular weight, with applications in enhanced oil recovery, as flocculants in water treatments, thickeners for coatings, and retention aids in papermaking. 

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