Abstract
Abstract Stereospecific, solution polymerization of butadiene to cis-1, 4 polybutadiene, using a catalyst system consisting of a cobalt compound and an organoaluminum compound, is a homogeneous reaction. In such a reaction, a diminution in catalyst activity accompanies the chain growth and chain transfer processes. Towards the end of the polymerization, the number of active catalyst centers is very small. The average molecular weight of polybutadiene can be raised in a definitive and reproducible manner, after completion of polymerization, by adding cocatalysts, e.g., alkyl or acyl halides, or certain active hydrogen compounds. Among other things, experiments in which (14C)-tert-butyl chloride was the cocatalyst have substantiated a cationic mechanism for this reaction. Changes in molecular structure are discussed on the basis of molecular weight fractionations with a Baker—Williams column and of results of viscometric and light scattering measurements.
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