Stereoregular diblock polybutadienes having a 1,4-cis/syndiotactic 1,2 structure from stereospecific polymerization

A process for the preparation of a stereoregular diblock polybutadiene composed of a polybutadiene block having a 1,4-cis structure and a polybutadiene block having a 1,2 syndiotactic structure, and having the following formula (I):

• PB1—PB2 (I)
• wherein:
• PB1 corresponds to the polybutadiene block having a 1,4-cis structure;
• and
• PB2 corresponds to the polybutadiene block having a 1,2 syndiotactic structure;
• wherein said stereoregular diblock polybutadiene has a content of 1,4-trans units of less than 3 mol %, with respect to a total molar quantity of butadiene units present in said stereoregular diblock polybutadiene,
• the process comprising:
• subjecting 1,3-butadiene to total or partial stereospecific polymerization in the presence of a catalytic system comprising at least one complex of cobalt including at least one imine nitrogen, in order to obtain polybutadiene with a 1,4-cis living structure;
• adding at least one monodentate aromatic phosphine and optionally 1,3-butadiene, and continuing said stereospecific polymerization, in order to obtain said stereoregular diblock polybutadiene composed of a polybutadiene block having a 1,4-cis structure and a polybutadiene block having a 1,2 syndiotactic structure.