Polymerization initiator, modified conjugated diene-based polymer, and methods for preparing them

A method for preparing a polymerization initiator, the method comprising:

• reacting a compound represented by the following Formula 1a and a compound represented by Formula 4 in a solvent to prepare a compound represented by Formula 1b (S1);
• and
• reacting the compound represented by Formula 1b and an alkali metal or a compound represented by the following Formula 5 (S2):
• in Formulae 1a and 1b,
• Cy is a cyclic saturated hydrocarbon group having from 5 to 8 carbon atoms, which is unsubstituted or substituted with an alkyl group having from 1 to 4 carbon atoms, A1′ and A2′ are each independently a functional group represented by the following Formula 2a, and A1″ and A2″ are each independently a functional group represented by the following Formula 2b:
• in Formulae 2a, 2b and 4,
• R is a linear hydrocarbon group having from 1 to 20 carbon atoms, or a monocyclic or multicyclic saturated hydrocarbon group having from 3 to 20 carbon atoms, X′ is a divalent hydrocarbon group having from 1 to 5 carbon atoms, a′ is 0 or 1, and X1 and X2 are each independently a halogen compound,
• R′(M)x [Formula 5]
• in Formula 5,
• R′ is a hydrocarbyl group having from 1 to 20 carbon atoms, M is an alkali metal, and x is an integer selected from 1 to 4.

A method for preparing a modified conjugated diene-based polymer, the method comprising:

• polymerizing conjugated diene-based monomers, or an aromatic vinyl-based monomer and a conjugated diene-based monomer in a hydrocarbon solvent including a polymerization initiator comprising a compound represented by the following Formula 1 to prepare an active polymer which is combined with an alkali metal (S3);
• and
• reacting the active polymer prepared in step (S3) with a modifier (S4):
• in Formula 1,
• Cy is a cyclic saturated hydrocarbon group having from 5 to 8 carbon atoms, which is unsubstituted or substituted with an alkyl group having from 1 to 4 carbon atoms, and A1 and A2 are each independently a functional group represented by the following Formula 2:
• in Formula 2,
• R is a linear hydrocarbon group having from 1 to 20 carbon atoms, or a cyclic saturated hydrocarbon group having from 3 to 20 carbon atoms, X is a divalent hydrocarbon group having from 1 to 5 carbon atoms, M is an alkali metal, and a is 0 or 1.

A modified conjugated diene-based polymer comprising a functional group derived from a polymerization initiator represented by the following Formula 1 at one terminal:

• in Formula 1,
• Cy is a cyclic saturated hydrocarbon group having from 5 to 8 carbon atoms, which is unsubstituted or substituted with an alkyl group having from 1 to 4 carbon atoms, and A1 and A2 are each independently a functional group represented by the following Formula 2:
• in Formula 2,
• R is a linear hydrocarbon group having from 1 to 20 carbon atoms, or a cyclic saturated hydrocarbon group having from 3 to 20 carbon atoms, X is a divalent hydrocarbon group having from 1 to 5 carbon atoms, M is an alkali metal, and a is 0 or 1.