Polymerization of acrylamides

Polyacrylamides are manufactured by free-radical polymerization of acrylamide to form chains of the stmcture shown, where n can range from several up to 400,000. 

Table 2. Chain-Transfer Constants for Polymerization of Acrylamide in Water...

Microemulsion Polymerization. Polyacrylamide microemulsions are low viscosity, non settling, clear, thermodynamically stable water-in-od emulsions with particle sizes less than about 100 nm (98—100). They were developed to try to overcome the inherent settling problems of the larger particle size, conventional inverse emulsion polyacrylamides. To achieve the smaller microemulsion particle size, increased surfactant levels are required, making this system more expensive than inverse emulsions. Acrylamide microemulsions form spontaneously when the correct combinations and types of oils, surfactants, and aqueous monomer solutions are combined. Consequendy, no homogenization is required. Polymerization of acrylamide microemulsions is conducted similarly to conventional acrylamide inverse emulsions. To date, polyacrylamide microemulsions have not been commercialized, although work has continued in an effort to exploit the unique features of this technology (100). 

Polymerization of acrylamide is usually performed in aqueous solutions. The principal factors that determine popularity of this polymerization technique are a high rate of polymer formation and the possibility to obtain a polymer with a large molecular weight. The reason for a specific effect produced by water upon acrylamide polymerization lies in protonation of the macroradical, leading to localization of an unpaired electron, which leads to an increase in the reactivity of the macroradical ... 

Acrylamide readily undergoes polymerization by conventional free radical methods, ionizing radiation, ultrasonic waves, and ultraviolet radiation. The base-cata-lized hydrogen transfer polymerization of acrylamide yields poly-/3-alanine (Nylon 3) a water insoluble polymer that is soluble in certain hot organics. All current industrial production is believed to be by free radical polymerization. 

Effects of the reaction medium on the radical polymerization of acrylamide have been examined in several reviews [13-15]. It has been shown that a change in the concentration of the monomer, the nature of the initia-... 

The polymerization of acrylamide in aqueous solutions in the presence of alkaline agents leads to the ob-tainment of partially hydrolyzed polyacrylamide. The polymerization process under the action of free radicals R (formed on the initiator decomposition) in the presence of OH ion formed on the dissociation of an alkali addition (NaOH, KOH, LiOH), and catalyzing the hydrolysis can be described by a simplified scheme (with Me = Na, K, Li) ... 

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. 

Radical copolymerization is used in the manufacturing of random copolymers of acrylamide with vinyl monomers. Anionic copolymers are obtained by copolymerization of acrylamide with acrylic, methacrylic, maleic, fu-maric, styrenesulfonic, 2-acrylamide-2-methylpro-panesulfonic acids and its salts, etc., as well as by hydrolysis and sulfomethylation of polyacrylamide Cationic copolymers are obtained by copolymerization of acrylamide with jV-dialkylaminoalkyl acrylates and methacrylates, l,2-dimethyl-5-vinylpyridinum sulfate, etc. or by postreactions of polyacrylamide (the Mannich reaction and Hofmann degradation). Nonionic copolymers are obtained by copolymerization of acrylamide with acrylates, methacrylates, styrene derivatives, acrylonitrile, etc. Copolymerization methods are the same as the polymerization of acrylamide. 

III. KINETICS OF RADIATION-INDUCED POLYMERIZATION OF ACRYLAMIDE IN AQUEOUS SOLUTION... 

The reported values for the exponent of the dose-rate for the polymerization rate in gamma radiation-induced copolymerization of acrylamide with methyl chloride salt of A, A -dimethylaminoethyl methacrylate (DMAEM-MC) in aqueous solution was found to be 0.8 [16]. However, the dose-rate exponent of the polymerization rate at a lower dose-rate was found to be slightly higher than 0.5 for gamma radiation-induced polymerization of acrylamide in aqueous solution [45,62]. 

By performing in situ the polymerization of acrylamide in water/AOT/toluene microemulsions, clear and stable inverse latexes of water-swollen polyacrylamide particles stabilized by AOT and dispersed in toluene have been found [192-194], It was shown that the final dispersions consist of two species of particles in equilibrium, surfactant-coated polymer particles (size about 400 A) with narrow size distribution and small AOT micelles (size about 30 A). 

Moore and Hemmens [119] studied the photosensitization of primaquine and other antimalarial agents. The drugs were tested for in vitro photosensitizing capability by irradiation with 365 nm ultraviolet light in aqueous solutions. The ability of these compounds to photosensitize the oxidation of 2,5-dimethylfuran, histidine, trypotophan, or xanthine, and to initiate the free radical polymerization of acrylamide was examined in the pH range 2 12. Primaquine does not have significant photochemical activity in aqueous solution. 

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

Polyacrylamide gel is the most commonly used type of support medium for gel electrophoresis, and polyacrylamide gel electrophoresis is simply known as PAGE. The gel is usually formed by polymerization of acrylamide and the cross-linking agent N, iV -methylene-bis-acrylamide (Bis) in the presence of ammonium persulfate (APS, initiator) and N, N, N, iV -tetramethyl-ethylenediamine (TEMED, accelerator). The total concentration of acrylamide... 

The kinetics of the oxidation of isopropylamine by diperiodatocuprate(III) complex ion have been studied and the results are consistent with a mechanism in which dissociation of one of the periodate ligands is followed by an adduct formation between [Cu(HIOg)] and isopropylamine. Polymerization of acrylamide indicated the participation of free radicals The kinetics of the oxidation of several diols by diperiodatocuprate(III) (DPC) in aqueous alkaline media have been studied. ... 

The polymerization of acrylamide (or methacrylamide) by strong bases such as sodium, orga-nolithium compounds, and alkoxides yields a polymer structure... 

The anionic polymerization of lactams proceeds by a mechanism analogous to the activated monomer mechanism for anionic polymerization of acrylamide (Sec. 5-7b) and some cationic polymerizations of epoxides (Sec. 7-2b-3-b). The propagating center is the cyclic amide linkage of the IV-acyllactam. Monomer does not add to the propagating chain it is the monomer anion (lactam anion), often referred to as activated monomer, which adds to the propagating chain [Szwarc, 1965, 1966]. The propagation rate depends on the concentrations of lactam anion and W-acy I lactam, both of which are determined by the concentrations of lactam and base. 

There have been efforts to enhance stereoselectivity in radical polymerization by using fluoroalcohols or Lewis acids that complex with monomers such as MMA and vinyl acetate [Isobe et al., 2000, 2001a Okamoto et al., 2002], In almost all instances the effects are nil or very small. For example, the use of perfluoro-t-butyl alcohol as solvent instead of toluene changes (rr) from 0.89 to 0.91 in the polymerization of MMA at —78°C. An exception is in the polymerization of acrylamide in the presence of some rare-earth Lewis acids such as ytterbium triflate. The polymer is atactic at 0°C, (m) = 0.46, in the absence of the Lewis acid, but significantly isotactic, (m) — 0.80, in the presence of the Lewis acid. The reason for this effect is unclear. More highly isoselective polymerization occurs in some radical polymerizations of MMA (Sec. 8-14b). 

Besides in the liquid phase, some polyreactions are also performed in the solid state, for example, the polymerization of acrylamide or trioxane (see Example 3-24). The so-called post condensation, for example, in the case of polyesters (see Example 4-3), also proceeds in the solid phase. Finally, ring closure reactions on polymers with reactive heterocyclic rings in the main chain (e.g., poly-imides, see Example 4-20) are also performed in the solid state. 

Polymerization of Acrylamide with a Redox System in Aqueous Solution... 

Fig. 11.2.2 Dependence of particle size on medium for precipitation polymerization of acrylamide, meihacrylic acid, and methylenebisacrylaniidc.

E. Uchida, Y. Uyama, and Y. Ikada, Surface graft polymerization of acrylamide onto poly(elliylene... 

Kamogawa, and Sekiya (54) studied the graft polymerization of acrylamide onto cotton fabric using ceric ammonium nitrate as the catalyst. Similarly to Kulkarni et al. (35) the authors performed subsequent cross-linking with formaldehyde amd methylol compounds. From precipitation studies by acidification of cuprammonium solutions on mixtures of polyacrylamide and cellulose on the one hand and polyacrylamide-cellulose grafts on the other the authors conclude that chemical bonds must exist between the two polymers in the grafted product. 

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