|155. Nakhmanovich, B.I.; Zolotareva, I.; Litvinenko, G. I.; Arest-Yakubovich, A.A.; Müller, A.H.E.: Anionic Polymerization of Butadiene Initiated by Tributyltin Sodium. Kinetic Analysis of Induction Periods Generated by Transfer to Initiator Precursor, Macromolecular Chemistry and Physics 202, 3536 (2001) -- DOI: 10.1002/1521-3935(20011201)202:18<3536::AID-MACP3536>3.0.CO;2-D|
|Stichworte: anionic polymerization; btadiene; chain transfer; initiators; kinetics|
The kinetics of anionic polymerization of butadiene initiated by a new bimetallic initiator, tributyltin sodium, was studied. The mechanism was found to depend on the nature of solvent. Whereas in toluene the polymerization kinetics is similar to that observed with common organosodium initiators, in the presence of THF the initiation rate is two orders of magnitude lower, the polymerization rate is three orders of magnitude lower, and a marked induction period appears. The explanation and kinetic analysis of the latter phenomenon is given, based on a chain transfer reaction to the initiator precursor, hexabutyldistannane, followed by fast regeneration of initiator. This scheme enables a good fit to the experimental data. From the calculations it follows that for the appearance of a prolonged induction period two conditions should be satisfied: slow initiation, ki M0/kpI0 < 1, and intensive chain transfer to precursor, ktr /kp 10. The Scheme proposed can be used for the explanation of induction periods in other anionic and group transfer polymerization processes.