Polymerization of vinyl monomers with salts of bronsted acids

The polymerization of vinyl monomers (N-phenylmaleimide, acrylamide, acrylonitrile, methyl vinyl ketone, methyl methacrylate, vinyl chloride, and styrene) with sodium salts of Brønsted acids (sodium cyanide, sodium nitrite, sodium hydroxide, etc.) were investigated at 0°C in dimethylformamide. N-Phenylmaleimide, acrylonitrile, and methyl vinyl ketone were found to undergo polymerization with sodium cyanide, however the other monomers were not polymerized with this salt. In the polymerizations of acrylonitrile and N-phenylmaleimide with sodium cyanide, the rates of the polymerizations were found to be proportinal to the initiator concentration and to the square of the monomer concentration. The activation energy of acrylonitrile polymerization was 3.7 kcal/mole, and that of N-phenylmaleimide ws 3.0 kcal/mole. The results of the copolymerization of acrylonitrile with methyl methacrylate at 0°C in dimethyl-formamide with sodium cyanide confirm that these polymerizations proceeded by an anionic mechanism initiated by the Michael addition reaction of the monomers with the salts. In these polymerizations, the monomer reactivity increased with increase in the e values. The initiation ability of sodium salts increased with increasing pK_a of the conjugate acids and with decreasing electronegativity of metal ion in the series of lithium, sodium, and potassium cyanide. The polymerizations took place only in aprotic polar solvents, and did not occur in weak polar solvents and in protonic solvents.