Polyacrylamide radical initiator

Commodity Chain-Growth Polymers. Two of the largest commodity wafer-soluble polymers are poly(vinyl alcohol) (PVA) and polyacrylamide (PAM). They are prepared by the free-radical initiation of vinyl monomers, a chain-growth polymerization technique. 

Polyacrylamide type flocculants are prepared by polymerization of acrylamide (AA) or by copolymerization it with some other monomers in water, organic or mixed (water and organic) solutions as well as emulsions in presence of radical initiators [2], AA can be distinguished from other mogomers by high polymerization activity [3] and molecules of... 

Polyacrylamide exhibits strong hydrogen bonding and water solubility. Most of the interest in this polymer is associated with this property. Polymerization of acrylamide monomer is usually conducted in an aqueous solution, using free-radical initiators and transfer agents. 

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) ... 

Elegant work by Van der Hoff [60] seems to suggest that it is the latter, or more correctly there is a Gaussian distribution about the midpoint of a chain. However, as to whether the main chains are primarily broken by ultrasonic action is still open to question since it is possible that the main chain scissions are secondary effects due to chemical reactions initiated by unstable intermediates, such as free radicals or ions, produced by sonication. For example McKay [61] has shown that hydroxyl radicals, generated by the oxidation of Fe by H2O2, are the cause of chain scission in polyacrylamide molecules in aqueous solution. 

Monomer and initiator must be soluble in the liquid and the solvent must have the desired chain-transfer characteristics, boiling point (above the temperature necessary to carry out the polymerization and low enough to allow for ready removal if the polymer is recovered by solvent evaporation). The presence of the solvent assists in heat removal and control (as it also does for suspension and emulsion polymerization systems). Polymer yield per reaction volume is lower than for bulk reactions. Also, solvent recovery and removal (from the polymer) is necessary. Many free radical and ionic polymerizations are carried out utilizing solution polymerization including water-soluble polymers prepared in aqueous solution (namely poly(acrylic acid), polyacrylamide, and poly(A-vinylpyrrolidinone). Polystyrene, poly(methyl methacrylate), poly(vinyl chloride), and polybutadiene are prepared from organic solution polymerizations. 

The irradiation of a mixture of two polymers A and Bn, either in the solid state or in solution, yields free radicals A and Z , which by recombination give the initial An and Bn polymers or by cross-addition a graft (or block) copolymer 4j,BQ. Although this method gives only very low yields of graft copolymers, it has nevertheless be applied by Hekg-lein in the system polyvinylpyrrolidone-polyacrylamide (102). 

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