Methods are described for the preparation of polymers using a lanthanide-based coordination catalyst and arresting polymerization using a reduced amount of a Lewis base while retaining the reactivity of the polymer chain ends toward functionalization agents. The Lewis base is a meso-enriched oxolanyl Lewis base. The resulting functionalized polymer has a higher level of purity and can be used in products such as tires.

A catalyst composition capable of forming a conjugated diene-based polymer having a narrow molecular weight distribution by being used in polymerization of a conjugated diene-based monomer, a method of preparing the same, a method of preparing a conjugated diene-based polymer using the catalyst composition, and a conjugated diene-based polymer prepared by the method of preparing the polymer are provided. Since the catalyst composition according to the present invention includes a polymer having a number-average molecular weight of 3,000 g/mol to 10,000 g/mol and including a conjugated diene-based monomer-derived unit, the catalyst composition may be used in the polymerization of a conjugated diene-based monomer to prepare a conjugated diene-based polymer having a narrower molecular weight distribution in comparison to a conventional neodymium catalyst composition.

Metallic complexes having indenyl ligands can be used as an ingredient of a catalyst system. The catalyst system can be used in polymerizations of ethylenically unsaturated hydrocarbon monomers that include both olefins and polyenes. Embodiments of the catalyst system can provide interpolymers that include polyene mer and from 40 to 75 mole percent ethylene mer, with a plurality of the ethylene mer being randomly distributed. The catalyst system also can be used in solution polymerizations conducted in C.sub.5-C.sub.12 alkanes, yielding interpolymers that include at least 10 mole percent ethylene mer.

Process for preparing a random butadiene-isoprene copolymer having a high content of cis-1,4 units comprising copolymerizing butadiene and isoprene, in the presence of at least one organic solvent, and a catalytic system prepared in situ comprising: (a.sub.1) at least one neodymium carboxylate soluble in said organic solvent, containing a variable amount of water, the H2O/Nd molar ratio being between 0.001/1 and 0.50/1; (a.sub.2) at least one aluminum alkyl compound; (a.sub.3) at least one aluminum alkyl compound containing at least one halogen atom. The random butadiene-isoprene copolymer having a high content of cis-1,4 units obtained from the abovementioned process may be advantageously used in a number of applications ranging from the modification of plastics [for example, obtainment of high impact polystyrene (HIPS)], to the production of tires, in particular the production of tire treads and/or of tire sidewalls.

A copolymer of a 1,3-diene and of an olefin selected from the group consisting of α-monoolefins, ethylene and mixtures thereof is provided. The copolymer bears, at one of its chain ends, an alkoxysilyl or silanol function, functional group F.sup.1, and the copolymer is different from a copolymer of a 1,3-diene and a vinylaromatic monomer.

The present invention relates to a modified conjugated diene-based polymer having a high modification ratio with improved compounding properties by being excellent affinity with a filler and a method for preparing the same. The modified conjugated diene-based polymer thus prepared includes a functional group derived from a compound represented by Formula 1 at one terminal, and has excellent affinity with a filler. If the modified conjugated diene-based polymer is applied to a rubber composition, excellent processability, tensile strength and viscoelasticity may be achieved.

Without significantly impacting monomer conversion, the cis-1,4 mer content of conjugated diene mer in polymers can be increased by adding one or more Lewis bases to a catalyst composition that includes a Group 3 metal atom-containing carboxylate. This effect can be seen even at above average monomer concentrations.

The present invention relates to a process for preparing high-reactivity isobutene homo- or copolymers with a content of terminal vinylidene double bonds per homo- or copolymer chain end of at least 70 mol % which comprises polymerizing isobutene or an isobutene-comprising monomer mixture in the presence of an aluminum trihalide-donor complex effective as a polymerization catalyst or of an alkylaluminum halide-donor complex, said complex comprising, as the donor, a mixture of at least two organic compounds with at least one ether function each.

The present invention relates to a process for preparing high-reactivity isobutene homo- or copolymers with a content of terminal vinylidene double bonds per homo- or copolymer chain end of at least 70 mol % which comprises polymerizing isobutene or an isobutene-comprising monomer mixture in the presence of an aluminum trihalide-donor complex effective as a polymerization catalyst or of an alkylaluminum halide-donor complex, said complex comprising, as the donor, a mixture of at least two organic compounds with at least one ether function each.

The present invention provides a catalyst composition including a functionalizing agent of the following Formula 1 together with a rare earth metal compound, an alkylating agent, and a halogen compound, having good catalytic activity and polymerization reactivity and useful for the preparation of a conjugated diene-based polymer having high linearity and excellent processability, and a conjugated diene-based polymer prepared using the catalyst composition
(X.sub.1).sub.a—Sn—(X.sub.2).sub.4-a  [Formula 1]
wherein, a, X.sub.1, and X.sub.2 are the same as defined in the disclosure.