Conjugated diene polymer and method for producing same, polymer composition, crosslinked product, and tire

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

• polymerizing a monomer comprising a conjugated diene compound in a presence of a metallic compound comprising an alkali metal or an alkaline earth metal, to thereby yield a conjugated diene-based polymer (I) having an active terminal;
• reacting the conjugated diene-based polymer (I) with compound [B] having 4 or more functional groups which can react with the active terminal, to thereby yield conjugated diene-based polymer (II);
• and
• performing a hydrogenation, so that a hydrogenation ratio of structural units derived from the conjugated diene compound comprised in the conjugated diene-based polymer (II) is adjusted to 65 to 97%,
• wherein the reacting is so that the conjugated diene-based polymer (II) contains a polymer comprising a multi-branched structure having 4 or more molecular chains in an amount of 25 to 75 mass %, and
• at least one species of the metallic compound and the compound [B] comprises at least one element selected from the group consisting of nitrogen, oxygen, and sulfur.