Emulsion miniemulsion

Heterogeneous polymerization processes (emulsion, miniemulsion, non-aqueous dispersion) offer another possibility for reducing the rate of termination through what are known as compartmcntalization effects. In emulsion polymerization, it is believed that the mechanism for chain stoppage within the particles is not radical-radical termination but transfer to monomer (Section 5.2.1.5). These possibilities have provided impetus for the development ofliving heterogeneous polymerization (Sections 9.3.6.6, 9.4.3.2, 9.5.3.6). 

In this review we summarize and discuss the amphiphilic properties of polyoxyethylene (PEO) macromonomers and PEO graft copolymer molecules, the aggregation of amphiphilic PEO macromonomers into micelles, the effect of organized aggregation of macromonomers on the polymerization process, and the kinetics of radical polymerization and copolymerization of PEO macromonomer in disperse (dispersion, emulsion, miniemulsion, microemulsion, etc.) systems [1-5]. 

The radical polymerization in disperse systems may be divided into several types according to the nature of continuous phase and the polymerization loci the dispersion, emulsion, miniemulsion, microemulsion, suspension, etc. 

Amphiphilic lipopeptides with a hydrophobic paraffinic chain containing from 12 to 18 carbon atoms and a hydrophilic peptidic chain exhibit lyotropic meso-phases and good emulsifying properties. The X-ray diffraction study of the mesophases and of dry lipopeptides showed the existence of three types of mesomorphic structures lamellar, cylindrical hexagonal and body-centred cubic. Two types of polymorphism were also identified one as a function of the length of the peptidic chain and the other as a function of the water content of the mesophases. The emulsifying properties of the lipopeptides in numerous pairs of immiscible liquids such as water/ hydrocarbons and water/base products of the cosmetic industry showed that small amounts of lipopeptides easily give three types of emulsions simple emulsions, miniemulsions and microemulsions. 

In the last few years, many efforts have been given to the preparation of magnetic latexes in dispersed media using suspension, precipitation, dispersion, emulsion, miniemulsion and microemulsion polymerizations. In this review chapter, the synthesis and functionalization of magnetic core-shell polymer particles in dispersed media have been reviewed with the main focus on emulsion polymerization. 

Finally, under well-defined conditions, it is possible to polymerize performed emulsion droplets. This is especially true for emulsions prepared by condensation methods where the conditions can be controlled in such a way that both secondary nucleation can be avoided and droplet or particle stability can be maintained during the entire polymerization. In the case of emulsions prepared by comminution techniques, suspension polymerization is a good example of a system where the (conditions) properties of emulsions can be converted into the corresponding properties of sols/suspensions. For smaller drop sizes, the solubility of the monomer in water is crucial, but unfortunately, very hydrophobic monomers are technically unimportant, at least nowadays. The addition of hydrophobic molecules needs tailored emulsification procedures regarding and DSD, and a certain maturation time to result in stable emulsions. Miniemulsion polymerization is a promising way, although the question as to what extent a 1 1 copy of an emulsion is possible is still waiting for an answer. 

This exclusion of polymers from the interior of the vesicles results in an osmotic compression of the water layers and a decrease in the water layer thickness and lamellar phase volume. This effect allows the control of bulk properties such as viscosity and also provides a probe of water layer dimensions in lamellar dispersions. The lamellar surfactant system used in this study is the sodium dodecyl sulfate (SDS)/dodecanol (Ci20H)/water system that has been used to prepare submicron diameter emulsions (miniemulsions) from monomers for emulsion polymerization (5) and for the preparation of artificial latexes by direct emulsification of polymer solutions such as ethyl cellulose (4). This surfactant system forms lamellar dispersions (vesicles) in water at very low surfactant concentrations (< 13 mM). 

Control of radical poljmerization with the addition of thiocarbonylthio compounds that serve as reversible addition fragmentation chain transfer (RAFT) agents was first reported in 1998. Since that time much research carried out in these laboratories and elsewhere has demonstrated that RAFT polymerization is an extremely versatile process.f It can be applied to form narrow polydispersity poljmers or copolymers from most monomers amenable to radical poljmerization. It is possible to take RAFT poljmerizations to high conversion and achieve commercially acceptable polymerization rates. Polymerizations can be successfully carried out in heterogeneous media (emulsion, miniemulsion, suspen-... 

Table 1 Summary and comparison of the important properties of conventional emulsions, miniemulsions, and microemulsions ...

Emulsion Type Conventional Emulsion Miniemulsion Microemulsion... 

Other Components. The smaller the particle size, at a given phase ratio, the more difficult it is to ensure colloidal stability (cf Fig. 5). This means that for aqueous heterophase polymerizations in the order suspension < microsuspension < emulsion < miniemulsion < microemulsion, the stabilizer concentration increases. Contrary to the simple polymerization of st5Tene in water, polymerization recipes for industrially important polymer dispersions comprise up to six monomers, frequently more than two emulsifiers, more than one initiating system, and a few other aids like biocides, defoaming agents, plasticizers for supporting film formation (39). The monomer-to-water ratio is adjusted in such a way that a solid content results typically between 40 and 60% or even higher. The amoimts of surfactants and initiator (mainly peroxodisulfate) are typically between 0.5 and 2% (w/w) relative to the monomers and 0.5% (w/w) relative to water, respectively. 

Simultaneous normal and reverse initiation (SR NI) ATRP (Fig. 1.17c) was developed to allow the precursors of highly active catalytic complexes to be added to the reaction in the higher oxidation state and at lower concentration. SR NI ATRP comprises a dual initiation system i.e. standard free radical initiators and initiators comprising a transferable atom or group in conjunction with the stable precursor of an active catalyst complex. This initiation system can be used to prepare any type of polymer that can be obtained by normal ATRP, and can be conducted in bulk, solution, emulsion, miniemulsion, and by heterogeneous polymerization. 

REACTIONS IN HETEROGENEOUS MEDIA EMULSION, MINIEMULSION, MICROEMULSION, SUSPENSION,... 

FIGURE 4.1 Schematic representation of microemulsion, emulsion, miniemulsion, and suspension polymerization. 

In the second chapter (Preparation of polymer-based nanomaterials), we summarize and discuss the literature data concerning of polymer and polymer particle preparations. This includes the description of mechanism of the radical polymerization of unsaturated monomers by which polymer (latexes) dispersions are generated. The mechanism of polymer particles (latexes) formation is both a science and an art. A science is expressed by the kinetic processes of the free radical-initiated polymerization of unsaturated monomers in the multiphase systems. It is an art in that way that the recipes containing monomer, water, emulsifier, initiator and additives give rise to the polymer particles with the different shapes, sizes and composition. The spherical shape of polymer particles and the uniformity of their size distribution are reviewed. The reaction mechanisms of polymer particle preparation in the micellar systems such as emulsion, miniemulsion and microemulsion polymerizations are described. The short section on radical polymerization mechanism is included. Furthermore, the formation of larger sized monodisperse polymer particles by the dispersion polymerization is reviewed as well as the assembling phenomena of polymer nanoparticles. 

Heterogeneous polymerization processes (emulsion, miniemulsion, nonaqueous dispersion) offer another possibility for reducing the rate of termination through what are known as compartmentalization effects. In emulsion polymerization, it is... 

References cited provide details of polymerization of the monomers indicated. Heterogeneous polymerizations (emulsion, miniemulsion) are indicated by the monomer being in italics. Monomer/RAF agent combinations that are relatively ineffective are indicated by the monomer being in parentheses. DMAM, A/,W-dimethylacrylamide EHA, 2-ethylhexyl acrylate HPMAM, /V-(2-hydroxypropyl) methacrylamide MAM, methacrylamide NIPAM, W-isopropyl acrylamide tBA, ferf-butyl acrylate VBz, vinyl benzoate. 

A/B copolymerization of monomer A with monomer B. Fleterogeneous polymerizations (emulsion, miniemulsion) are indicated by the monomer being in italics. A-b-B block copolymers are triblocks. 

ROMP has been reported in emulsion, miniemulsion, dispersion, and suspension. Caution should be used in interpreting reported process types in the literature however, these various processes are not as well defined for nonradical polymerizations as they are for radical polymerizations. In particular, the locus of chain initiation is sometimes ambiguous and the mechanisms of particle nucleation may not be well understood. 

The anionic polymerization in aqueous dispersed systems concerns mainly the alkyl cyanoacrylate monomers, which can polymerize spontaneously at a very fast rate in the presence of water. (Nano)partides and nanocapsules were synthesized by emulsion, miniemulsion, or inverse miniemulsion polymerization processes. They mainly find applications in the biomedical domains and received for that reason a huge interest which makes it impossible to be exhaustive in this chapter. 

Much has been written on RAFT emulsion, miniemulsion and dispersion polymerization. The first communication on RAFT polymerization... 

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