Chain Transfer in Anionic Polymerization

The process of chain transfer has received very little quantitative study insofar as the anionic systems are concerned. The first study of an anionic chain transfer process was that of Robertson and Marion on the polymerization of 1,3-butadiene by sodium in toluene. The reaction of toluene with the sodium active center led to the formation of benzyl sodium. This work was the first to demonstrate the important role of solvent in transfer reactions involving anionic active centers  

The ability of toluene to serve as a transfer agent was further demonstrated by Bower and McCormick and Brooks for the organosodium initiated polymerization of styrene in that solvent. Both groups reported molecular weights lower than the values calculated from the monomer-initiator ratio. 

Higginson and Wooding also reported a transfer reaction to solvent for the case of the polymerization styrene in ammonia initiated by potassium amide. There was no termination event in their kinetic scheme, i.e., active center deactivation via a spontaneous termination event was not considered to be a significant event. 

Gatzke has investigated the chain transfer process involving toluene and poly(styryl)lithium at 60 °C. A relationship between the number-average degree of polymerization and the transfer constant was derived  

The transfer reaction of butadiene with the sodium counterion in a tetrahydro-furan-toluene solution was studied The presence of the ether was found to 

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