Stereospecific polymerization of 2‐substituted‐1,3‐butadienes. I. Crystalline polymers of 2‐tert‐butyl‐1,3‐butadiene

Some results obtained in the stereospecific polymerization of 2‐tert‐butyl‐1,3‐butadiene are reported. The catalysts employed were prepared from TiCl4 and aluminum alkyls or soluble aluminum hydride derivatives. Polymers thus obtained were crystalline with a melting point of 106°C. and soluble in common solvents. X‐ray investigation shows the polymer to have a helical chain structure built on 11 monomeric units with cis configuration, distributed on three turns. The identity period along the chain axis is 15.3 A. A comparison of the infrared spectra of the crystalline and amorphous polymers is given. Attempts to obtain a crystalline 1,4‐trans polymer failed; this is in accord with the lower stability of such a configuration due to steric repulsion of the bulky group.