TRANSFORMATION REACTIONS IN POLYMERIZATION SYSTEMS .2. ANIONIC-POLYMERIZATION TO FREE-RADICAL POLYMERIZATION BY USE OF LEAD SALTS

In Part I of this series, a method was outlined by which a polymeric anion could be transformed via a three-stage process into a carbenium ion so that cationic polymerication could then ensure and novel block copolymers could be prepared. In this paper, methods are presented for transforming an anionic terminal group into a free radical. Again, an intermediate stage is required which allows isolation and re-solution of the initially formed homopolymer in an appropriate solvent before introducing the second monomer and generating the free radicals. In contrast to the carbenium ion system, however, the transformation reaction should not be as fast as possible, but should be carefully controlled to match the kinetic characteristics of the free-radical polymerization process. Procedural details are given and experimental results are discussed in terms of mechanisms of transformation reactions in which lead compound has been used in termination reactions for intermediates (polymer-lead triethyl adducts).