Numerical Simulations of Nanogel Synthesis Using Pulsed Electron Beam

In this work, a new method for numerical simulation of the radiation chemistry of aqueous polymer solutions exposed to a sequence of electron pulses is presented. The numerical simulations are based on a deterministic approach encompassing the conventional homogeneous radiation chemistry of water as well as the chemistry of polymer radicals. The multitude of possible reactions in the macromolecular system is handled by allowing for a large number of macromolecular species. The speciation of macromolecular species is done to account for variations in molecular weight, number of alkyl radicals per chain, number of peroxyl radicals per chain, number of oxyl radicals per chain, and number of internal loops. As benchmarking, previously published results from a series of experiments on pulsed irradiation of aqueous poly(N-vinylpyrrolidone) (PVP) solutions are used. The numerical simulations clearly show that the pulsed nature of the radiation must be accounted for. The simulations qualitatively reproduce the experimentally observed impact of initial gas saturation (air and N2O) and polymer concentration on the molecular chain length upon irradiation. The formation of double bonds as a function of dose as well as the impact of effective dose rate on the final chain length are also qualitatively reproduced in the simulations.