Activated monomer 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. 

The monomers (acrylamide, acrylic acid, and methacrylamide) and the redox activators (ferrous ammonium sulfate and cuprous chloride) were used as received. 

The patent and open literature were searched for examples of dye sensitized photopolymerization in which a common monomer (acrylamide), and one of several common dyes (thionine, T methylene blue, MB or rose bengal, RB) were used in combination with a stated concentration of an activator. The polymerization conditions (monomer concentration, light intensity absorbed, and extent conversion) were stated in each case chosen for inclusion. The relative photospeed of the system was calculated based on several corrections to the raw data. We here define the relative photospeed of a composition as the inverse of the exposure time t needed to effect some fixed percentage of monomer conversion. 

The UV-active monomers chosen as hydrophobes in this study are shown in Chart I. The saturated analogs to the acrylamides, 1 and 2, were the propionamides, 3 and 4, respectively. These analogs were the corresponding model compounds that represented the chromophoric functionality of the hydrophobe when incorporated into a polymer backbone. The polymer systems chosen for this initial attempt to quantify hydrophobe incorporation were copolymers of the hydrophobes and acrylamide (RAM) and their partially hydrolyzed analogs (HRAM), which are terpolymers of hydrophobe, acrylamide, and acrylate. 

The mechanism of RAFT polymerization relies on activation of the monomer double bond to enable efficient fragmentation from the intermediate radical, which in turn provides control over the molecular weight of the resulting polymer. It follows that vinyl monomers, for which the double bond is not activated, are still challenging to polymerize efficiently via RAFT. Although attempts have been made to control the polymerization of 1-alkenes [16] and allyl butyl ethers [17], as yet only copolymerization with active monomers (acrylates and acrylamides) has led to a... 

The propagating center is neither an ion nor a radical, but a carbon to carbon double bond at the end of the chain. The monomer anion adds to this double bond. This process is a step-growth polymerization and the monomer anion is called an activated monomer. Not all acrylamide polymerizations, initiated by strong bases, however, proceed by a hydrogen transfer process. Depending upon reaction conditions, such as solvent, monomer concentration, and temperature some polymerizations can take place through the carbon to carbon double bonds [216]. 

The polymerization of methyl methacrylate in acidic solution by iron metal was reported earlier [213]. Palit and co-workers [214] studied the mechanism of methyl methacrylate in the presence of ferric chloride. They proposed that the hydroxyl radical formed by the chemical decomposition of the system containing ferric salt is the active species for initiating polymerization. Narita et al. reported [215] the polymerization of acrylamide initiated by ferric nitrate and suggested that a complex of monomer and metallic salt generates an active monomer radical capable of initiating vinyl polymerization. 

The more-activated monomers (MAMs, see Figure 6.6) are those where the double bond is conjugated to an aromatic ring e.g., styrene (St), 4-vinyl pyridine (4VP), acenaphthalene (AcN)), a carbonyl group e.g., methyl methacrylate (MMA), methyl acrylate (MA), acrylamide (Am), A-acryloyl morpholine (NAM), maleic anhydride (MAH)) or a nitrile e.g., acrylonitrile (AN)). 

Chain-Growth Associative Thickeners. Preparation of hydrophobically modified, water-soluble polymer in aqueous media by a chain-growth mechanism presents a unique challenge in that the hydrophobically modified monomers are surface active and form micelles (50). Although the initiation and propagation occurs primarily in the aqueous phase, when the propagating radical enters the micelle the hydrophobically modified monomers then polymerize in blocks. In addition, the hydrophobically modified monomer possesses a different reactivity ratio (42) than the unmodified monomer, and the composition of the polymer chain therefore varies considerably with conversion (57). The most extensively studied monomer of this class has been acrylamide, but there have been others such as the modification of PVAlc. Pyridine (58) was one of the first chain-growth polymers to be hydrophobically modified. This modification is a post-polymerization alkylation reaction and produces a random distribution of hydrophobic units. 

Acrylamide, C H NO, is an interesting difiinctional monomer containing a reactive electron-deficient double bond and an amide group, and it undergoes reactions typical of those two functionalities. It exhibits both weak acidic and basic properties. The electron withdrawing carboxamide group activates the double bond, which consequendy reacts readily with nucleophilic reagents, eg, by addition. 

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. 

Radiation Treatment NVP, 2-hydroxyethylmethacrylate (HEMA), and acrylamide (AAm) have been grafted to the surface of ethylene-propylene-diene monomer (EPDM) rubber vulcanizates using the radiation method (from a Co 7 source) to alter surface properties such as wettability and therefore biocompatibility [197]. Poncin-Epaillard et al. [198] have reported the modification of isotactic PP surface by EB and grafting of AA onto the activated polymer. Radiation-induced grafting of acrylamide onto PE is very important... 

Homopolymers and copolymers from amido-sulfonic acid or salt containing monomers can be prepared by reactive extrusion, preferably in a twin screw extruder [1660]. The process produces a solid polymer. Copolymers of acrylamide, N-vinyl-2-pyrrolidone, and sodium-2-acrylamido-2-methyl-propane sulfonate have been proposed to be active as fluid loss agents. Another component of the formulations is the sodium salt of naphthalene formaldehyde sulfonate [207]. The fluid loss additive is mixed with hydraulic cements in suitable amounts. 

In order to incorporate polar-functionalized olefins, the catalyst system must exhibit tolerance to the functionality as described above. Therefore, polar monomer incorporation by the Ni(II) catalysts is generally not observed. Traces of methyl acrylate can be incorporated by the Ni(II) catalyst only under low loadings of that monomer [85], Acrylamide has been incorporated after prior treatment with tri-isobutylaluminum to block the amide donor sites, although polymerization activities are still relatively low [86], A similar protection of Lewis-basic functionalities by the coactivator has been cited to explain the copolymerization of certain monomers by early transition metal systems as well [40],... 

A variety of monomers, including styrene, acrylonitrile, (meth) acrylates, (meth) acrylamides, 1,3-dienes, and 4-vinylpyridine, undergo ATRP. ATRP involves a multicomponent system of initiator, an activator catalyst (a transition metal in its lower oxidation state), a deactivator (the transition state metal in its higher oxidation state) either formed spontaneously or deliberately added, ligands, and solvent. Successful ATRP of a specific monomer requires matching the various components so that the dormant species concentration exceeds the propagating radical concentration by a factor of 106. 

For a variety of arylsulfinate salts containing para-substituents of varying electron demand, it was shown under controlled polymerization conditions (1 M acrylamide monomer, pH 7, 4 x 10 3 M activator for methylene blue sensitization) (43b) that dye bleaching occurred with a quantum yield of 0.10-0.17 and that quantum yields for monomer loss were 1200-1700. The efficiency of the dye bleaching and the polymerization reaction increased as the electron donor ability of the sulfinate increased. ... 

Enolates. Another class of activators for photoreducible dyes was discovered by Chaberek (24,45). Enolates of diketones such as acetylacetone or dimedone (5,5-dimethyl-l,3-cyclohex-anedione) were shown to be effective reductants for the excited states of MB and to polymerize monomers such as acrylamide. Chaberek, Shepp, and Allen discussed the mechanism of this process in a series of papers (46,47). 

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