Metal-free Carbanion Salts as Initiators for the Anionic Polymerization of Acrylic and Methacrylic Acid Esters

Molecular weights of up to 20 000 are attained in the polymerization of butyl acrylates with the malonates 1; the ratio of weight average molecular weight to number average molecular weight is ≤ 1.3. The likewise metal‐free salts 2 and 3 also smoothly polymerize acrylic esters in THF or toluene at room temperature. The explanation for this behavior, which differs from that of the corresponding sodium or potassium salts, could be that metal ions are necessary as activators for the typical terminating reactions of anionic polymerization. Compounds 1–3 are readily accessible and may be stored for months at 0 °C.