The blocky structure of Ziegler–Natta “random” copolymers: myths and experimental evidence

The crystallization behavior of butene–ethylene random isotactic copolymers prepared with a Ziegler–Natta catalyst, in particular the surprising crystallization of form II of isotactic polybutene in samples with a high ethylene concentration, provides novel evidence of the long-debated blocky molecular structure of these “random” copolymers.