Dynamic nuclear polarization of electron-beam irradiated polyethylene by pairs of alkyl free radicals

► We compare DNP of irradiated polyethylene (e-PE) with TEMPO-doped polystyrene (T-PS). ► Both growth and decay rates increase with square of radical concentration in T-PS. ► But, those rates increase linearly with the concentration in e-PE. ► e-PE is polarized by radical pairs. ► Higher polarization is expected by controlling inter-radical distance in the pairs in e-PE.