Bulk copolymerization of butadiene and isoprene was studied with homogeneous catalyst system: Nd(naph)3-Al(i-Bu)2H-CH3SiHCl3. It was shown that the polymerization conversion and [η] of the polymers obtained depended on the catalyst level and the molar ratio of AlH/ Nd. The catalyst system had high activity when the molar ratio of Cl/Nd was in the range of 1-4. The polymerization activity decreased with the increasing of butadiene ratio in the monomers. DSC showed that these polymers obtained had only one glass transition temperature. It was indicated that the product were true copolymers and not the mixture of the homopoly-mers

The structure and composition of the copolymers were determined with IR and 1H-NMR.The cis-1

4 content of the two monomer units in the copolymers was higher than 96%

and the molar ratio of the two monomer units was similar to the monomer feed ratio.The performance test of the raw and vulcanizated rubber were carried out.