The radical cyclization reactions of models for the growing radical chains formed from N,N-diallylamine (1), N-methyl-N,N-diallylamine (2), N,N-diallylammonium (3), N-methyl-N,N-diallylammonium (4) and N,N-dimethyl-N,N-diallylammonium (5) have been investigated computationally by DFT theory, using the B3LYP functional. Models formed by hydrogen atom addition to dienes 1-5 undergo five-membered ring cyclization reactions with activation energies predicted to be 7.2, 5.0, 8.6, 6.4, and 6.2 kcal/mol, respectively. Methyl substitution on nitrogen decreases the barrier to cyclization. One methyl has a larger effect on the cyclization rate than the second methyl. This rate enhancement is attributed to a decrease in gauche interactions in the transition state as compared to the initial structure and to different destabilizing effects when an H is replaced by a methyl group. These predicted rate effects are in agreement with the experimental data on polymerization efficiencies.