AbstractSome results are reported on the alkyllithium‐initiated polymerization of butadiene in cyclopentane in presence of 2,′2‐bis(4,4,6‐trimethyl‐1,3‐dioxane). The effect of this lithium chelating agent on one‐unit model active centres is also reported. Comparisons are made with another highly efficient polymer structure modifier, 1,2‐dipiperidinoethane. Conclusions are reached on the reasons why both are particularly effective in inducing the formation of polydienes having extremely hig