Anionic chain polymerization acrylamide

It might be noted that most (not all) alkenes are polymerizable by the chain mechanism involving free-radical intermediates, whereas the carbonyl group is generally not polymerized by the free-radical mechanism. Carbonyl groups and some carbon-carbon double bonds are polymerized by ionic mechanisms. Monomers display far more specificity where the ionic mechanism is involved than with the free-radical mechanism. For example, acrylamide will polymerize through an anionic intermediate but not a cationic one, A -vinyl pyrrolidones by cationic but not anionic intermediates, and halogenated olefins by neither ionic species. In all of these cases free-radical polymerization is possible. 

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... 

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. 

In the polymerization of the ion monomer pairs (which is carried out in aqueous solution) the cationic moieties (MPTMA+ or MPDMA+) and the anionic moiety (AMPS ) could have similar Q and e values, since they are the derivatives of acrylamide, resulting in a random incorporation of these units into the chain. Under these circumstances, a resulting network of ionically cross-linked chains seemed possible. Indeed, initially, hydrogels were formed in the polymerization of the monomer pairs of MPTMA AMPS and MPDMA AMPS. 

As a companion to the biguanide main-chain polymers, acrylic polymers with biguanide pendant groups were also sjmthesized (Figure 19) (polymer Cll). Polymers were synthesized by free radical polymerization, both as homopolymers and as copolymers of the biguanide monomer with acrylamide. MIC values for these polymers were substantially higher than for the monomer. The authors hypothesized that these results may be due to the fact that the polymers complex with anionic components in the culture media. As a comparison to this... 

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]. 

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