The role of molecular oxygen in the formation of radiation-engineered multifunctional nanogels

•Radiation-engineered nanogels are a nanoplatform for drug delivery.•Experiments and kinetic modeling of radiation-induced synthesis of nanogels are combined.•A new code is developed for aqueous systems subjected to sequences of electron pulses.•Experimental and simulation results reveal the crucial role of transient O2 on final polymer architecture.•Double bonds produced by disproportionation and scission reactions are quantified for the first time.