High cis-1,4 block copolymers of polybutadiene and polyisoprene

A method of preparing a vulcanizable composition including a high 1,4-cis block copolymer of polybutadiene and polyisoprene comprising:

• (i) forming a polymerization mixture that includes a pseudo-living polymer by combining a first monomer and a lanthanide-based catalyst, where the lanthanide-based catalyst comprises
• (a) a lanthanide-containing compound,
• (b) an aluminoxane,
• (c) an organoaluminum compound defined by the formula AlRnX3-n where each R is individually a hydrocarbon group or a substituted hydrocarbon group, each X is individually a hydrogen atom, a carboxylate group, an alkoxide group, or an aryloxide group, and where n is an integer of 1 to 3, and
• (d) a halogen-containing compound;
• (ii) adding a second monomer to the polymerization mixture that includes a pseudo-living polybutadiene polymer, to obtain the high 1,4-cis block copolymer of polybutadiene and polyisoprene;
• (iii) mixing the high 1,4-cis block copolymer of polybutadiene and polyisoprene with a filler and a curing agent to form the vulcanizable composition, wherein the high 1,4-cis block copolymer of polybutadiene and polyisoprene is between 50% and 100% by weight of a total rubber component of the vulcanizable composition;
• and
• where the first monomer is either 1,3-butadiene or isoprene and where the second monomer is not the same as the first monomer and is either 1,3-butadiene or isoprene.

A method of preparing a vulcanizable composition including a high 1,4-cis block copolymer of polybutadiene and polyisoprene comprising:

• (i) polymerizing 1,3-butadiene with a lanthanide-based catalyst to form a pseudo-living polymer, where the lanthanide-based catalyst comprises
• (a) a lanthanide-containing compound,
• (b) an aluminoxane,
• (c) an organoaluminum compound defined by the formula AlRnX3-n, where each R is individually a hydrocarbon group or a substituted hydrocarbon group, each X is individually a hydrogen atom, a carboxylate group, an alkoxide group, or an aryloxide group, and where n is an integer of 1 to 3, and
• (d) a halogen-containing compound;
• (ii) reacting the pseudo-living polymer with isoprene, to obtain the high 1,4-cis block copolymer of polybutadiene and polyisoprene, where the high 1,4-cis block copolymer of polybutadiene and polyisoprene has a ratio of polybutadiene to polyisoprene of from 80:20 to 20:80, and where polybutadiene blocks in the high 1,4-cis block copolymer of polybutadiene and polyisoprene have a cis-1,4-linkage content of greater than 96%, where the percentage is based upon the number of butadiene mer units adopting the cis-1,4 linkage versus the total number of butadiene mer units;
• (iii) mixing the high 1,4-cis block copolymer of polybutadiene and polyisoprene with a filler and a curing agent to form the vulcanizable composition, wherein the high 1,4-cis block copolymer of polybutadiene and polyisoprene is between 50% and 100% by weight of a total rubber component of the vulcanizable composition.