Metal-Free Activation in the Anionic Ring-Opening Polymerization of Cyclopropane Derivatives

The successful activation observed when using ButP4 phosphazene base and thiophenol or bisthiols for the anionic ring opening polymerization (ROP) of di-n-propyl cyclopropane-1,1- dicarboxylate is described. Well-defined monofunctional or difunctional polymers with a very narrow molecular weight distribution were obtained through a living process. Quantitative end-capping of the propagating malonate carba- nion was accessible by using either an electro- philic reagent such as allyl bromide or a strong acid such as HCl. Kinetics studies demonstrated a much higher reactivity compared to the conven- tional route using alkali metal thiophenolates.