Study on the mechanism of anionic polymerization with mixed RLi-R'OK initiators, 2 - Theoretical study of random styrene-butadiene copolymerization

Styrene-butadiene copolymerization using mixed RLi-R'OK initiators was mode lled on the basis of a traditional two-state scheme which supposes separate polymerization via lithium and potassium active species accompanied by a f ast exchange of their counter-ions. Copolymer composition and the monomer-c opolymer composition curves were calculated with respect to the influence o f the K/Li ratio. Furthermore, the influence of the initial RLi concentrati on on the K/Li ratio for an azeotropic copolymerization was investigated. N one of the proposed relations were found to agree with the published experi mental data. Therefore, similar to butadiene homopolymerization, styrene-bu tadiene copolymerization using an alkyllithium - potassium alkoxide initiat or can be rather explained by an one-state polymerization process under the participation of complex bimetallic centres than by a two-state process vi a individual oganometallic compounds.