Anionic polymerization of acrylamide

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. 

A reversed case is found, in which the matrix polymers are formed from the reinforcing rodlike molecule [23] PPTA polyanion was used as the initiator for the anionic polymerization of acrylamide to form the nylon 3 matrix. Composite films showed greatly improved strength and modulus over unmodified nylon 3 with no loss of flexibility. The combination of various chemical reactions will bring many possibilities. 

Experimental work on molecular composites has focused on attempting to kinetically delay the phase separation with a desirable morphology before the thermodynamics leads to complete immiscibility. Most of this work was initially performed as part of a program sponsored by the United States Air Force. For example, poly (p-phenylene terephthalamide) (PPTA) and poly (p-phenylene benozbisthiazole) (PBT) have been successfully dispersed in a Nylon 66 matrix.i 22 J y gf 23 reported that there are interactions present in a PPTA and Nylon 6 system and that phase separation can be thermally induced in molecular composites based on these two polymers. Thermally induced phase separation has also been observed in the PBT/ Nylon 6 system, when the melting temperature of the Nylon component is reached. Finally, Moore and Mathias reported a unique method for the preparation of molecular composites using an in situ polymerization process in which the anion of the PPTA was used as the initiator for the anionic polymerization of acrylamide in the formation of a Nylon 3 matrix. 

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. 

High-molecular-weight polymers of low polydispersity are formed [180]. BuONa initiates the isomerization polymerization of acrylamide, producing poly ( -alanine) (see also Chap. 5, Sect. 6.6). This initiation can be described as addition of the CH2=CHCONH anion to the monomer double bond [181]. The anion is formed by the reversible reaction... 

Trossarelli et al. studied the formation of poly-/ -alanine by the polymerization of acrylamide with ter/.-BuNa. The initiating anion is in equilibrium with the monomer [24]... 

Metal salts and complexes continue to attract interest as radical/ionic initiators. Trisoxalatoferrate/amine anion salts have been studied as initiators of the polymerization of acrylamide. Here the anion salts react with photolytically formed COa " radicals by an electron transfer mechanism to give photoactive initiating phenyl radicals by the set of reactions shown in Scheme 9. Ferric o-phenanthroline has been shown to be a good photoinitiator for... 

Helix-sense-selective anionic polymerization of acrylates TrA (32) and PDBSA (33)97 98 and acrylamides including the series of A/A -diphenylacrylamides" 101 (34) have been investigated using (+)-PMP, (—)-Sp,... 

Gross and coworkers examined the influence of surfactants on the peroxidase-initiated polymerization of acrylamide [21]. Irrespective of the nature of surfactant (cationic, anionic, neutral), they found a significant rate acceleration,... 

A brief review of the radical and anionic polymerization of allyl acrylate and allyl acrylamides has appeared in Spanish [85]. 

Anionic polymerization of unsubstituted acrylamide, catalyzed by strong bases, does not yield typical vinyl polymers. Instead, the product is a 1,3-adduct, poly -alanine). " Two alternate reaction paths were originally proposed " ... 

Anionic polymerization of lactams offers the best approach to the preparation of polyamide containing block copolymers. Styrene-nylon 6 block copolymers were prepared by adding e-caprolactam to polystyrene macroanions terminated with bisphenol A bis(chlorofor-mate)(31). Yamashita prepared ABA block copolymers of styrene-a-pyrrolidone and styrene- -caprolactam by sequential addition to styrene macroanions( ). Similarly Stehlik and Sebenda prepared N-acrylamide containing block copolymers(33). Block copolymers of isoprene-pivalolactam have also been reported( . In these cases the lactam was added to "living" polyisoprene anions. 

Acrylamide monomer is a white crystal, available commercially as a 50 wt % aqueous solution. Acrylamide monomer can be polymerized to a very-high-molecular-weight (lO -lO g/mole) homopolymer, copolymer, or terpolymer. Polyacrylamide (PAM) is a nonionic polymer. The anionic polyacrylamide species can be obtained from the hydrolysis of the amide (—CONH ) functional group of the homopolymer, or from the copolymerization of acrylamide with an anionic monomer, such as acrylic acid (AA) or 2-acrylamino 2-methyl propane sulfonic acid (AMPS). Acrylamide can be copolymerized with a cationic monomer, such as dimethyl diallylammonium chloride (DMDAAC) or acryloyloxyethyl trimethyl ammonium chloride (AETAC), to form the cationic acrylamide polymer. Acrylamide can simultaneously react with anionic and cationic monomers to form a polyampholyte. The acrylamide homopolymer, copolymers, and terpolymers are synthesized (1-20) by free radicals via solution or emulsion or other polymerization methods. F. A. Adamsky and E. J. Beckman (21) reported the inverse emulsion polymerization of acrylamide in supercritical carbon dioxide. The product classes of acrylamide polymers include liquid, dry, and emulsion. 

Method of synthesis hydrogen transfer polymerization of acrylamide in the presence of anionic catalyst vinyl polymerization is side reaction, which can be prevented if tert-BuOK catalyst is finely dispersed in polymerization solvents Masamoto, J, Memoirs of Fukui University of Technology, 3,1,291, 2003. 

Poly(P-alanine) (PA3) cannot be obtained by chemically initiated ROP of the unsubstituted azetidin-2-one (p-lactam), but only by anionic isomerization polymerization of acrylamide. The latter synthesis, however, generally leads to stmcturally irregular polyamide 3. On the contrary, the polymerization of p-lactams may be accessible by novel enzymatic routes. 

Breslow et al. reported that nylon-3 ( sometimes described as nylon 3 or poly- p -alanine) is obtained using hydrogen transfer polymerization of acrylamide in the presence of an anionic catalyst ... 

Pramanick and Sankar [99] investigated the polymerization of methyl methacrylate polymerization initiated by only ceric ions and found that the mechanism of initiation depends strongly on the acidity of the medium and is independent of the nature of anion associated with the ceric ion. In a moderately acidic medium, the primary reaction is the formation of hydroxyl radical by ceric-ion oxidation of water. When ceric sulfate is used, the hydroxyl radicals initiate the polymerization and appear as end groups in the polymer molecule. If, on the other hand, ceric ammonium sulfate or a mixture of ceric sulfate and ammonium sulfate are used, some of the hydroxyl radicals react with the ammonium ion, producing ammonium radicals, and both radicals act as initiators, giving polymers with both hydroxyl and amino end groups. In the polymerization of acrylamide by ceric salt, the infrared (IR) spectra suggests the formation of monomer-ceric salt complexes in aqueous solution [98]. This coordination bond presumably consists of both... 

Developing stereocontrol for the radical polymerization of acrylamides and methacrylamides is of particular interest, as accessing the corresponding poly (acrylamides) and poly(methacrylamides) by ionic or coordination polymerization is in some instances difficult or even impossible. Unsubstituted and monosubstituted acrylamides cannot be synthesized by anionic or... 

Acrylamides represent still another interesting class of monomers.6 Their anionic polymerization may be initiated by strong bases, like, e.g., amides. The growing chain contains the unit —CH2—CH —CO—NH2 and intramolecular proton transfer competes efficiently with its carbanionic growth. Since the rearrangement... 

Photopolymerization of acrylamide by the uranyl ion is said to be induced by electron transfer or energy transfer of the excited uranyl ion with the monomer (37, 38). Uranyl nitrate can photosensitize the polymerization of /S-propiolactone (39) which is polymerized by cationic or anionic mechanism but not by radical. The initiation mechanism is probably electron transfer from /S-propiolactone to the uranyl ion, producing a cation radical which propagates as a cation. Complex formation of uranyl nitrate with the monomer was confirmed by electronic spectroscopy. Polymerization of /J-propiolactone is also photosensitized by sodium chloroaurate (30). Similar to photosensitization by uranyl nitrate, an election transfer process leading to cationic propagation has been suggested. 

Anionic Catalysis Several bulky methacrylates afford highly isotactic, optically active polymers having a single-handed helical structure by asymmetric polymerization. The effective polymerization mechanism is mainly anionic but free-radical catalysis can also lead to helix-sense-selective polymerization. The anionic initiator systems can also be applied for the polymerization of bulky acrylates and acrylamides. The one-handed helical polymethacrylates show an excellent chiral recognition ability when used as a chiral stationary phase for high-performance liquid chromatography (HPLC) [97,98]. 

One of the best examples for discussing biotransformations in neat solvents is the enzymatic hydrolysis of acrylonitrile, a solvent, to acrylamide, covered in Chapter 7, Section 7.1.1.1. For several applications of acrylamide, such as polymerization to polyacrylamide, very pure monomer is required, essentially free from anions and metals, which is difficult to obtain through conventional routes. In Hideaki Yamada s group (Kyoto University, Kyoto, Japan), an enzymatic process based on a nitrile hydratase was developed which is currently run on a commercial scale at around 30 000-40 000 tpy with resting cells of third-generation biocatalyst from Rhodococcus rhodochrous J1 (Chapter 7, Figure 7.1). 

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