NOVEL INITIATING SYSTEMS FOR THE LIVING POLYMERIZATION OF ACRYLATES AND METHACRYLATES

The polymerization of methyl methacrylate with lithiated initiators in the presence of aluminium alkyls in toluene has living character but it deviates from conventional first-order kinetics and the polymers ha ve fairly broad molecular weight distributions. This results from the formation and precipitation of a coordinative polymer network in which the lithium ions of the living chain ends are coordinated to the in-c hain ester carbonyl groups. Thus, the network formation can be prevent ed by adding Lewis bases like methyl pivalate which coordinate to the living chain ends instead of the polymer. Alternatively, one can intro duce tetraalkylammonium salts aiming at an exchange of the lithium ion by a less electropositive cation. Both approaches lead to linear firs t-order time conversion plots for the polymerization of methacrylates and acrylates and to narrow molecular weight distributions, i.e., to a living and controlled polymerization. With these new initiating syste ms, various block and graft copolymers can be synthesized.