A method for the bulk treatment of polymeric materials is proposed. Energetic ions created after capture of a neutron beam by constituent atoms located within the polymer can be used to cause radiation‐induced modifications such as cross linking in the polymer. In contrast to traditional ion implantation, the proposed method enables bulk treatment because of the relatively deep penetration of neutrons. Analytical estimates and Monte Carlo computations are performed for the10B(n,&agr;)7Li reaction for the cross linking and hydrogen depletion of boron‐doped polystyrene. Requirements for the polymer composition and microstructure, as well as potential synthesis methods are discussed. ©1996 American Institute of Physics.