Chelating polymer granules prepared by radiation-induced homopolymerization. I - Kinetic study of radiation polymerization process

Chelating polymer granules containing amidoxime chelating groups were synth esized by radiation-induced homopolymerization of acrylonitrile monomer. Th e chemical reactive intermediate polyacrylonitrile was treated with hydroxy lamine solution to convert the chemical active cyano groups into the amidox ime groups. Kinetic study of the effects of monomer concentration, radiatio n dose, dose rate, and temperature on the polymerization process was invest igated. It was found that at low monomer concentration, the rate of polymer ization is roughly independent on the initial monomer concentration, while at high monomer concentration, 35-65%, a marked acceleration on the rate wa s observed. The order of the dependence of the initial rate of polymerizati on on the dose rate is 0.77, which deviates from the classical square-root law due to the precipitation of the formed polymer. The conversion percent and molecular weight of the produced polymer are inversely proportional to dose rate at constant radiation dose. The activation energy was found to be 2.7 kcal/mol, and the rate constant of initiation is independent of temper ature. The effect of type of solvent on the polymerization was studied. DMF solvent of the closest solubility parameter to the solubility parameter of polyacrylonitrile is the best solvent for the polymerization process. (C) 2000 John Wiley & Sons, Inc.