Acrylamide emulsion polymerization

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. 

The emulsion polymerization of acrylamide yields a high-molecular polymer (with the molecular weight reaching 2.5-10 ), which can be easily dispersed in water to obtain water-in-oil type latex (containing 30-60% polymer). On prolonged storage, the emulsion exhibits lamination, but subsequent stirring allows easy redispersal of the product. 

DSEP direct soapless emulsion polymerization, SSEC seeded soapless emulsion copolymerization, DDC direct dispersion copolymerization, TDSC two-stage dispersion copolymerization, ATES Allyl trietoxysilane, VTES vinyl trietoxysilane, DMAEM dimethylaminoethyl-methacrylate, CMS chloromethylstyrene, GA glutaraldehyde, AAc Acrylic acid Aam Acrylamide HEMA 2-hydroxyethylmethacrylate. 

MAIs may also be formed free radically when all azo sites are identical and have, therefore, the same reactivity. In this case the reaction with monomer A will be interrupted prior to the complete decomposition of all azo groups. So, Dicke and Heitz [49] partially decomposed poly(azoester)s in the presence of acrylamide. The reaction time was adjusted to a 37% decomposition of the azo groups. Surface active MAIs (M, > 10 ) consisting of hydrophobic poly(azoester) and hydrophilic poly(acrylamide) blocks were obtained (see Scheme 22) These were used for emulsion polymerization of vinyl acetate—in the polymerization they act simultaneously as emulsifiers (surface activity) and initiators (azo groups). Thus, a ternary block copolymer was synthesized fairly elegantly. 

Fig. 10. Amide end-capped poly(hexafluoropropy-lene oxide) used for the inverse emulsion polymerization of acrylamide in C02 [123]...

Emulsion polymerization was first employed during World War II for producing synthetic rubbers from 1,3-butadiene and styrene. This was the start of the synthetic rubber industry in the United States. It was a dramatic development because the Japanese naval forces threatened access to the southeast Asian natural-rubber (NR) sources, which were necessary for the war effort. Synthetic mbber has advanced significantly from the first days of balloon tires, which had a useful life of 5000 mi to present-day tires, which are good for 40,000 mi or more. Emulsion polymerization is presently the predominant process for the commercial polymerizations of vinyl acetate, chloroprene, various acrylate copolymerizations, and copolymerizations of butadiene with styrene and acrylonitrile. It is also used for methacrylates, vinyl chloride, acrylamide, and some fluorinated ethylenes. 

In the conventional emulsion polymerization, a hydrophobic monomer is emulsified in water and polymerization initiated with a water-soluble initiator. Emulson polymerization can also be carried out as an inverse emulsion polymerization [Poehlein, 1986]. Here, an aqueous solution of a hydrophilic monomer is emulsified in a nonpolar organic solvent such as xylene or paraffin and polymerization initiated with an oil-soluble initiator. The two types of emulsion polymerizations are referred to as oil-in-water (o/w) and water-in-oil (w/o) emulsions, respectively. Inverse emulsion polymerization is used in various commerical polymerizations and copolymerizations of acrylamide as well as other water-soluble monomers. The end use of the reverse latices often involves their addition to water at the point of application. The polymer dissolves readily in water, and the aqueous solution is used in applications such as secondary oil recovery and flocculation (clarification of wastewater, metal recovery). 

A special procedure is reverse emulsion polymerization. In this case, a hydrophilic monomer (e.g., acrylamide) is dissolved in water and the resulting solution is emulsified using special water-in-oil emulsifiers in a water-immiscible organic liquid (petroleum ether). Then the polymerization is initiated with a... 

These superabsorbents are synthesized via free radical polymerization of acrylic acid or its salts in presence of a crosslinker (crosslinking copolymerization). Initiators are commonly used, water-soluble compounds (e.g., peroxodi-sulfates, redox systems). As crosslinking comonomers bis-methacrylates or N,hT-methylenebis-(acrylamide) are mostly applied. The copolymerization can be carried out in aqueous solution (see Example 5-11 or as dispersion of aqueous drops in a hydrocarbon (inverse emulsion polymerization, see Sect. 2.2.4.2). 

Initiators -for acrylamide [ACRYLAMIDE POLYMERS] (Vol 1) -anionic initiators [INITIATORS - ANIONIC INITIATORS] (Voll4) -cationic initiators [INITIATORS - CATIONIC INITIATORS] (Vol 14) -in emulsion polymerization [LATEX TECHNOLOGY] (Vol 15) -for fluorocarbon elastomers [ELASTOMERS, SYNTHETIC - FLUOROCARBON ELASTOMERS] (Vol 8) -Free-radical initiators [INITIATORS - FREE-RADICAL INITIATORS] (Voll4) -organohthium compounds as [LITHIUM AND LITHIUM COMPOUNDS] (Vol 15) -peroxides as [PEROXIDES AND PEROXIDE COMPOUNDS - INORGANIC PEROXIDES] (Vol 18) -for propylene oxide [PROPYLENE OXIDE] (Vol 20) -for PUR polyols [POLYETHERS - PROPYLENE OXIDE POLYMERS] (Vol 19) -of suspension polymerization [ACRYLIC ESTER POLYMERS - SURVEY] (Vol 1)... 

Adamsky, F. A. Beckman, E. J. Inverse Emulsion Polymerization of Acrylamide in Supercritical Carbon Dioxide. Macromolecules 1994, 27, 312. 

Glukhikh V, Graillat C, Pichot C (1987) Inverse emulsion polymerization of acrylamide. II. Synthesis and characterization of copolymers with methacrylic acid. J Polym Sci Polym Chem Ed 25(4) 1127-1161... 

The concentrated emulsion polymerization was also applied to an aqueous solution of acrylamide dispersed in decane. Compared to the conventional inverse emulsion polymerization [20], a much smaller amount of organic solvent is employed to produce polymer latexes. 

Fig. 25. Conversion as a function of time (in the concentrated emulsion polymerization ( ). in the solution polymerization (O)) (acrylamide 12 g, water 28 g, sorbitan monooleate 1.0 ml, decane 2.5 ml, K2S2Oe 2.5 x 10 4 g, 40 °C, nitrogen atmosphere)...

It is important to emphasize that the concentrated emulsion polymerization of acrylamide in water leads to latexes of submicrometer size and employs a very small amount of organic solvent as compared to the conventional emulsion polymerization. 

In addition to the practical interest, the process presents challenges encouraging further fundamental exploration. A thorough study not reported here, has been performed on the mechanism and kinetics of the polymerization of acrylamide in AOT/water/toluene microemulsions (Carver, M.T.r Dreyer, U. Knoesel, R. Candau, F. Fitch, R.M. J. Polym. Sci. Polym. Chem. Ed., in press. Carver, M.T. Candau, F. Fitch, R.M. J. Polym. Sci. Polym. Chem. Ed., in press). The termination reaction of the polymerization was found to be first order in radical concentration, i.e. a monoradical reaction instead of the classical biradical reaction. Another major conclusion was that the nucleation of particles is continuous all throughout the polymerization in contrast to conventional emulsion polymerization where particle nucleation only occurs in the very early stages of polymerization. These studies deserve further investigations and should be extended to other systems in order to confirm the unique character of the process. 

Polymer nanoparticles including nanospheres and nanocapsules (Fig. 1) can be prepared according to numerous methods that have been developed over the last 30 years. The development of these methods occurred in several steps. Historically, the first nanoparticles proposed as carriers for therapeutic applications were made of gelatin and cross-linked albumin. Then, to avoid the use of proteins that may stimulate the immune system and to limit the toxicity of the cross-linking agents, nanoparticles made from synthetic polymers were developed. At first, the nanoparticles were made by emulsion polymerization of acrylamide and by dispersion polymerization of methylmethacry-late.f These nanoparticles were proposed as adjuvants for vaccines. However, since they were made of non-biodegradable polymers, these nanoparticles were rapidly substituted by particles made of biodegradable... 

Inverse Emulsion Polymerization of Acrylamide in Near-Critical and Supercritical Continuous Phases... 

After the paper making process is complete, latexes that are useful as binders for the application of clays or CaCC>3 to paper for printing paper may be prepared using the dimer of AMS. In a typical formulation, styrene, butadiene, Me methacrylate, and acrylonitrile were emulsion polymerized in the presence of AMS dimer to obtain a copolymer latex.473 Surprisingly, the AMS dimer was used in combination with tert-dodecylmercaptan, so there may have been some residual odor. Unsaturated carboxylic acids, such as acrylic acid, or sulfonic acids, such as 2-ethylsulfonyl acrylate, or unsaturated amides, such as acrylamide, are also useful, providing the polarity necessary in these applications.474... 

Emulsion polymerization typically refers to the polymerization of a nonaqueous material in water. The polymerization of a water-soluble material in a nonaqueous continuum has been called inverse emulsion polymerization. The inverse emulsion polymerization technique is used to synthesize a wide range of polymers for a variety of applications such as wall paper adhesive, waste water fiocculant, additives for oil recovery fluids, and retention aids. The emulsion polymerization technique involves water-soluble polymer, usually in aqueous solution, emulsified in continuous oil phase using water in oil emulsifier. The inverse emulsion is polymerized using an oil- or water-soluble initiator. The product is a colloidal dispersion of sub-microscopic particles with particle size ranging from 0.05 to 0.3 pm. The typical water-soluble monomers used are sodium p-vinyl benzene sulfonate, sodium vinyl sulfonate, 2-sulfo ethyl acrylate, acrylic acid, and acrylamide. The preferred emulsifiers are Sorbitan monostearate and the oil phase is xylene. The proposed kinetics involve initiation in polymer swollen micelles, which results in the production of high molecular weight colloidal dispersion of water-swollen polymer particles in oil. 

A few years later, Blaschke designed purely synthetic chiral stationary phases obtained by emulsion polymerization of acrylamides prepared from amino acids [17]. These phases had been developed for preparative purposes and proved to be very efficient for the preparative resolution of various chiral drugs for which the enantiomers have been isolated for the first time. These earher applications include the separation of the enantiomers of the sadly well-known drug thalidomide (Fig. 6.2) [18],... 

DADMAC/Acrylamide Copolymer (75/25 Wt %)-Emulsion Polymerization. The following were added to the reaction vessel 64.4 parts benzene, 15 parts DADMAC, 5 parts acrylamide, 13.5 parts deionized H20, and 2 parts sodium octyl phenoxyethoxy-2-ethanol sulfate. The vessel was purged for 1 hr with N2 at 50° 1°C after which 5 ppm Fe+2 and 2 X 10"3 mol f-butylperoxypivalate/mol monomer were added. The temperature was held at 50° 1°C for 20 hr. The product, isolated via acetone precipitation, was found to be a DADMAC/acrylamide copolymer (60/40 wt %). 

Howdle et al. was the first to report on the enzymatic emulsion polymerization of water-soluble acrylamide monomers in a w/c microemulsion [75]. Acrylamide is one of the few monomers that show limited solubility in supercritical C02, and hence was particularly suited to inverse emulsion polymerization [61]. In this report, Howdle et al. showed that the yields and molecular weights obtained via polymerization in C02 are comparable to those generated in a conventional polymerization in an alkane/water medium. Indeed, polymer molecular weights up to 900 kDa were observed when a surfactant was not used and molecular weights around 300 kDa when a perfhiropolyether was used. The generally accepted mechanism for this reaction is shown in Figure 13.5. 

Inverse emulsion polymerization of acrylamide in supercritical carbon dioxide. Macromolecules, 27 (1),... 

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