Synthesis of Low Molecular Weight Butadiene Polymers Using Cationic Catalytic Systems Based on Diethylaluminum Chloride

The cationic polymerization of butadiene under the action of catalytic systems based on diethylaluminum chloride (AlEt2Cl) in combination with tertiary alkyl halides (AHs) such as tert-butyl chloride, tert-butyl bromide, and 2-chloro-2-methylbutane is found to be an efficient method for the preparation of fully soluble butadiene polymers at a technologically convenient process temperature of 20°C. It is shown that with an increase in the duration of butadiene polymerization process, the weight-average molecular weights and polydispersity of the polymer increase significantly with a simultaneous decrease in the unsaturation of polybutadiene, which is associated with the transfer reaction of the growing chain to the double bond of the polymer during polymerization. A 13C NMR spectral study showed that the macromolecules of polybutadiene synthesized on the AlEt2Cl–tert-butyl chloride catalytic system consist mainly of 1,4-trans units and contain two types of initial tert-butyl units and two types of end chlorine-containing units formed as a result of the transfer reaction of the growing chain to tert-butyl chloride. Based on the data of 13C NMR spectra of polybutadiene, a method for calculating butadiene conversion during polymerization is developed, and a mechanism of the process of cationic polymerization of butadiene is proposed. It is shown that the synthesized "cationic" polybutadiene is characterized by high film-forming properties and can be a promising component in the production of paints and varnishes.