Production method for branched conjugated diene-based polymer, production method for rubber composition, production method for tire, branched conjugated diene-based polymer, and branched conjugated diene-based polymer composition

A production method for a branched conjugated diene-based polymer, comprising the following sequential steps:

• (i) a polymerizing step of obtaining a conjugated diene-based polymer having an active end by polymerizing or copolymerizing a conjugated diene compound, or a conjugated diene compound and an aromatic vinyl compound with an organic lithium-based compound used as a polymerization initiator;
• (ii) a branching step of introducing a branch structure by reacting a styrene derivative as a branching agent with the active end of the conjugated diene-based polymer, wherein the active end reacts with a vinyl group and a functional group of the styrene derivative, respectively, and the active end reacted with the vinyl group polymerizes with the conjugated diene compound and/or the aromatic vinyl compound while retaining a polymerization activity;
• (iii) adding a second conjugated diene compound and/or a second aromatic vinyl compound to a reaction system during and/or after the branching step such that the second conjugated diene compound and/or the second aromatic vinyl compound reacts with the active end of the conjugated diene-based polymer;
• and
• (iv) a reaction step of reacting a coupling agent containing silicon and a sulfur atom with the active end of the conjugated diene-based polymer resulting from the branching step.