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

Abstract

Сationic polymerization of butadiene with the catalytic systems based on diethylaluminium chloride (AlEt2Cl) in combination with tertiary alkyl halides (AH), such as tert-butyl chloride, tert-butyl bromide and 2-chloro-2-methylbutane, is an effective method for obtaining fully soluble butadiene polymers at a industrially relevant temperature of 20°C. It is shown that, regardless of the nature of AH in the catalytic system, with an increase in the duration of the polymerization process of butadiene, the values of the weight-average molecular weight and polydispersity of the polymers significantly increase with the simultaneous decrease of polybutadiene unsaturation, which is associated with the transfer reaction of the growing chain to the polymer double bond during polymerization. Using the 13C NMR spectroscopy method, it was found that polybutadiene macromolecules synthesized on the AlEt2Cl–tert-butyl chloride catalytic system consist mainly of 1,4-trans units, 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 the conversion of butadiene during polymerization has been developed, and a mechanism of the process of cationic butadiene polymerization has been 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 paint and varnish materials.