The copolymerization of ethylene and 1

3-butadiene with rare earth catalysts was investigated. It was found that ethylene and 1

3-butadiene were copolymerized to give high molecular weight products. Solvents extraction of crude copolymer indicated that there was no polyethylene but about 8% polybutadiene was present. The products obtained have been confirmed to be copolymers containing long ethylene-ethylene sequence by DSC

X-ray diffraction and electron microscope. Butadiene unit in the copolymer was almost exclusively in cis-1

4 structure. X-ray crystallinity was of polyethylene type with a slight variation of the structure parameters. Melting temperature

crystallinity and crystallite size increased with increasing ethylene unit content.