Slereospecific copolymers 1,3‐butadiene‐2‐phenylbutadiene

The results obtained in the stereospecific copolymerization of 1,3‐butadiene with 2‐phenylbutadiene are reported. The copolymers were generally obtained using catalysts prepared from substituted aluminum hydrides, AlI3 and TiCl4. Homopolymerization of 2‐phenylbutadiene with such catalysts gives an amorphous, low M.W. polymer having prevailing 1,4‐cis structure. In the copolymers the 2‐phenylbutadiene units still have a substantially cis structure; also the butadiene units are mainly 1,4‐cis up to 90‐95%. The 1,2 content in the copolymers is always very low. The content of 2‐phenylbutadiene units in the copolymers varies in a broad range from 10 to 80% and the reaction rate and the average molecular weight diminish as the phenylbutadiene increases. The monomer reactivity ratios were calculated and the distribution of sequence lengths in the copolymer chains was made by statistical analysis. The copolymer composition was determined by IR and NMR analysis and the results compared with spectra obtained from mechanical mixtures of the homopolymers. The formation of a true copolymer was confirmed by extractions, fractionations, and glass transition temperature determinations. Mechanical properties of the copolymers are given and compared with those of other polymers, in particular with those of 1,4‐cis polybutadiene.